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	$79.92	3.565%	$82.7691	$82.77	$82.75	$82.80
Purchase #2	$125.25	5.126%	$131.6703	$131.67	$131.65	$131.70
Purchase #3	$159.51	12.161%	$178.908	$178.91	$178.90	$178.90
Purchase #4	$120.43	9.437%	$131.795	$131.80	$131.80	$131.80
Purchase #5	$192.72	4.534%	$201.4579	$201.46	$201.45	$201.50
Purchase #6	$238.76	6.431%	$254.1147	$254.11	$254.10	$254.10
Purchase #7	$58.75	11.411%	$65.454	$65.45	$65.45	$65.50
7 purchase totals =	$975.34		$1,046.1690	$1,046.17	$1,046.10	$1,046.30