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	$197.58	4.406%	$206.2854	$206.29	$206.30	$206.30
Purchase #2	$128.51	11.370%	$143.1216	$143.12	$143.10	$143.10
Purchase #3	$56.32	3.816%	$58.4692	$58.47	$58.45	$58.50
Purchase #4	$249.57	5.873%	$264.2272	$264.23	$264.25	$264.20
Purchase #5	$79.56	3.836%	$82.6119	$82.61	$82.60	$82.60
Purchase #6	$168.26	12.390%	$189.1074	$189.11	$189.10	$189.10
Purchase #7	$53.90	4.764%	$56.4678	$56.47	$56.45	$56.50
7 purchase totals =	$933.70		$1,000.2905	$1,000.30	$1,000.25	$1,000.30