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	$102.90	8.107%	$111.2421	$111.24	$111.25	$111.20
Purchase #2	$137.37	10.411%	$151.6716	$151.67	$151.65	$151.70
Purchase #3	$104.27	6.634%	$111.1873	$111.19	$111.20	$111.20
Purchase #4	$137.99	5.222%	$145.1958	$145.20	$145.20	$145.20
Purchase #5	$232.77	4.490%	$243.2214	$243.22	$243.20	$243.20
Purchase #6	$86.81	11.404%	$96.7098	$96.71	$96.70	$96.70
Purchase #7	$201.67	4.489%	$210.723	$210.72	$210.70	$210.70
7 purchase totals =	$1,003.78		$1,069.9510	$1,069.95	$1,069.90	$1,069.90