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	$198.77	6.224%	$211.1414	$211.14	$211.15	$211.10
Purchase #2	$128.33	11.336%	$142.8775	$142.88	$142.90	$142.90
Purchase #3	$79.45	11.123%	$88.2872	$88.29	$88.30	$88.30
Purchase #4	$228.73	6.494%	$243.5837	$243.58	$243.60	$243.60
Purchase #5	$88.90	7.783%	$95.8191	$95.82	$95.80	$95.80
Purchase #6	$80.59	11.668%	$89.9932	$89.99	$90.00	$90.00
Purchase #7	$214.96	8.481%	$233.1908	$233.19	$233.20	$233.20
7 purchase totals =	$1,019.73		$1,104.8929	$1,104.89	$1,104.95	$1,104.90