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	$19.41	7.208%	$20.8091	$20.81	$20.80	$20.80
Purchase #2	$66.32	7.561%	$71.3345	$71.33	$71.35	$71.30
Purchase #3	$187.36	3.563%	$194.0356	$194.04	$194.05	$194.00
Purchase #4	$206.98	10.721%	$229.1703	$229.17	$229.15	$229.20
Purchase #5	$25.83	7.108%	$27.666	$27.67	$27.65	$27.70
Purchase #6	$119.91	6.539%	$127.7509	$127.75	$127.75	$127.80
Purchase #7	$185.62	3.102%	$191.3779	$191.38	$191.40	$191.40
7 purchase totals =	$811.43		$862.1443	$862.15	$862.15	$862.20