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	$61.86	9.690%	$67.8542	$67.85	$67.85	$67.90
Purchase #2	$220.38	3.578%	$228.2652	$228.27	$228.25	$228.30
Purchase #3	$157.96	6.178%	$167.7188	$167.72	$167.70	$167.70
Purchase #4	$157.63	8.185%	$170.532	$170.53	$170.55	$170.50
Purchase #5	$83.73	6.437%	$89.1197	$89.12	$89.10	$89.10
Purchase #6	$85.32	8.128%	$92.2548	$92.25	$92.25	$92.30
Purchase #7	$163.89	8.285%	$177.4683	$177.47	$177.45	$177.50
7 purchase totals =	$930.77		$993.2130	$993.21	$993.15	$993.30