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	$140.86	6.714%	$150.3173	$150.32	$150.30	$150.30
Purchase #2	$105.40	11.441%	$117.4588	$117.46	$117.45	$117.50
Purchase #3	$6.71	3.443%	$6.941	$6.94	$6.95	$6.90
Purchase #4	$223.96	4.649%	$234.3719	$234.37	$234.35	$234.40
Purchase #5	$38.91	7.600%	$41.8672	$41.87	$41.85	$41.90
Purchase #6	$57.95	12.702%	$65.3108	$65.31	$65.30	$65.30
Purchase #7	$107.43	3.429%	$111.1138	$111.11	$111.10	$111.10
7 purchase totals =	$681.22		$727.3808	$727.38	$727.30	$727.40