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	$66.48	4.131%	$69.2263	$69.23	$69.25	$69.20
Purchase #2	$151.44	13.498%	$171.8814	$171.88	$171.90	$171.90
Purchase #3	$36.68	11.536%	$40.9114	$40.91	$40.90	$40.90
Purchase #4	$214.94	12.647%	$242.1235	$242.12	$242.10	$242.10
Purchase #5	$148.77	10.618%	$164.5664	$164.57	$164.55	$164.60
Purchase #6	$159.64	13.831%	$181.7198	$181.72	$181.70	$181.70
Purchase #7	$117.80	11.782%	$131.6792	$131.68	$131.70	$131.70
7 purchase totals =	$895.75		$1,002.1080	$1,002.11	$1,002.10	$1,002.10