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	$223.67	4.275%	$233.2319	$233.23	$233.25	$233.20
Purchase #2	$89.44	5.625%	$94.471	$94.47	$94.45	$94.50
Purchase #3	$159.80	12.703%	$180.0994	$180.10	$180.10	$180.10
Purchase #4	$228.81	9.165%	$249.7804	$249.78	$249.80	$249.80
Purchase #5	$111.47	6.650%	$118.8828	$118.88	$118.90	$118.90
Purchase #6	$245.51	8.563%	$266.533	$266.53	$266.55	$266.50
Purchase #7	$106.69	5.507%	$112.5654	$112.57	$112.55	$112.60
7 purchase totals =	$1,165.39		$1,255.5639	$1,255.56	$1,255.60	$1,255.60