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	$155.33	7.231%	$166.5619	$166.56	$166.55	$166.60
Purchase #2	$122.28	7.353%	$131.2712	$131.27	$131.25	$131.30
Purchase #3	$229.33	5.576%	$242.1174	$242.12	$242.10	$242.10
Purchase #4	$173.54	13.286%	$196.5965	$196.60	$196.60	$196.60
Purchase #5	$88.59	12.772%	$99.9047	$99.90	$99.90	$99.90
Purchase #6	$56.61	10.627%	$62.6259	$62.63	$62.65	$62.60
Purchase #7	$240.35	6.267%	$255.4127	$255.41	$255.40	$255.40
7 purchase totals =	$1,066.03		$1,154.4903	$1,154.49	$1,154.45	$1,154.50