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	$130.25	10.354%	$143.7361	$143.74	$143.75	$143.70
Purchase #2	$229.64	4.574%	$240.1437	$240.14	$240.15	$240.10
Purchase #3	$185.78	5.664%	$196.3026	$196.30	$196.30	$196.30
Purchase #4	$48.69	3.529%	$50.4083	$50.41	$50.40	$50.40
Purchase #5	$47.47	12.819%	$53.5552	$53.56	$53.55	$53.60
Purchase #6	$46.63	12.440%	$52.4308	$52.43	$52.45	$52.40
Purchase #7	$120.73	6.778%	$128.9131	$128.91	$128.90	$128.90
7 purchase totals =	$809.19		$865.4898	$865.49	$865.50	$865.40