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	$45.56	6.538%	$48.5387	$48.54	$48.55	$48.50
Purchase #2	$55.61	7.371%	$59.709	$59.71	$59.70	$59.70
Purchase #3	$72.81	3.703%	$75.5062	$75.51	$75.50	$75.50
Purchase #4	$245.74	9.274%	$268.5299	$268.53	$268.55	$268.50
Purchase #5	$244.70	5.125%	$257.2409	$257.24	$257.25	$257.20
Purchase #6	$168.53	11.857%	$188.5126	$188.51	$188.50	$188.50
Purchase #7	$172.76	10.124%	$190.2502	$190.25	$190.25	$190.30
7 purchase totals =	$1,005.71		$1,088.2875	$1,088.29	$1,088.30	$1,088.20