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	$91.33	6.505%	$97.271	$97.27	$97.25	$97.30
Purchase #2	$104.47	3.112%	$107.7211	$107.72	$107.70	$107.70
Purchase #3	$190.67	7.693%	$205.3382	$205.34	$205.35	$205.30
Purchase #4	$92.32	8.248%	$99.9346	$99.93	$99.95	$99.90
Purchase #5	$75.63	5.635%	$79.8918	$79.89	$79.90	$79.90
Purchase #6	$196.69	13.168%	$222.5901	$222.59	$222.60	$222.60
Purchase #7	$172.46	9.508%	$188.8575	$188.86	$188.85	$188.90
7 purchase totals =	$923.57		$1,001.6043	$1,001.60	$1,001.60	$1,001.60