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	$129.32	6.530%	$137.7646	$137.76	$137.75	$137.80
Purchase #2	$52.32	3.557%	$54.181	$54.18	$54.20	$54.20
Purchase #3	$56.80	8.145%	$61.4264	$61.43	$61.45	$61.40
Purchase #4	$248.74	6.146%	$264.0276	$264.03	$264.05	$264.00
Purchase #5	$215.28	12.297%	$241.753	$241.75	$241.75	$241.80
Purchase #6	$236.38	11.850%	$264.391	$264.39	$264.40	$264.40
Purchase #7	$136.54	6.838%	$145.8766	$145.88	$145.90	$145.90
7 purchase totals =	$1,075.38		$1,169.4202	$1,169.42	$1,169.50	$1,169.50