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	$140.77	5.321%	$148.2604	$148.26	$148.25	$148.30
Purchase #2	$59.88	6.476%	$63.7578	$63.76	$63.75	$63.80
Purchase #3	$42.77	9.737%	$46.9345	$46.93	$46.95	$46.90
Purchase #4	$29.46	11.383%	$32.8134	$32.81	$32.80	$32.80
Purchase #5	$119.43	7.263%	$128.1042	$128.10	$128.10	$128.10
Purchase #6	$61.61	9.424%	$67.4161	$67.42	$67.40	$67.40
Purchase #7	$151.68	9.589%	$166.2246	$166.22	$166.20	$166.20
7 purchase totals =	$605.60		$653.5110	$653.50	$653.45	$653.50