Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$163.37	12.313%	$183.4857	$183.49	$183.50	$183.50
Purchase #2	$140.84	10.589%	$155.7535	$155.75	$155.75	$155.80
Purchase #3	$237.60	11.311%	$264.4749	$264.47	$264.45	$264.50
Purchase #4	$134.95	11.768%	$150.8309	$150.83	$150.85	$150.80
Purchase #5	$235.66	6.435%	$250.8247	$250.82	$250.80	$250.80
Purchase #6	$47.82	12.608%	$53.8491	$53.85	$53.85	$53.80
Purchase #7	$174.38	11.740%	$194.8522	$194.85	$194.85	$194.90
7 purchase totals =	$1,134.62		$1,254.0710	$1,254.06	$1,254.05	$1,254.10