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	$243.36	8.814%	$264.8098	$264.81	$264.80	$264.80
Purchase #2	$243.75	5.508%	$257.1758	$257.18	$257.20	$257.20
Purchase #3	$102.72	8.347%	$111.294	$111.29	$111.30	$111.30
Purchase #4	$115.45	11.154%	$128.3273	$128.33	$128.35	$128.30
Purchase #5	$55.56	6.756%	$59.3136	$59.31	$59.30	$59.30
Purchase #6	$226.49	13.132%	$256.2327	$256.23	$256.25	$256.20
Purchase #7	$106.26	6.750%	$113.4326	$113.43	$113.45	$113.40
7 purchase totals =	$1,093.59		$1,190.5858	$1,190.58	$1,190.65	$1,190.50