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	$165.89	9.655%	$181.9067	$181.91	$181.90	$181.90
Purchase #2	$33.90	9.524%	$37.1286	$37.13	$37.15	$37.10
Purchase #3	$161.43	6.441%	$171.8277	$171.83	$171.85	$171.80
Purchase #4	$59.25	11.197%	$65.8842	$65.88	$65.90	$65.90
Purchase #5	$246.74	3.236%	$254.7245	$254.72	$254.70	$254.70
Purchase #6	$151.44	9.144%	$165.2877	$165.29	$165.30	$165.30
Purchase #7	$124.82	3.742%	$129.4908	$129.49	$129.50	$129.50
7 purchase totals =	$943.47		$1,006.2502	$1,006.25	$1,006.30	$1,006.20