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	$116.66	9.187%	$127.3776	$127.38	$127.40	$127.40
Purchase #2	$219.51	13.112%	$248.2922	$248.29	$248.30	$248.30
Purchase #3	$54.35	7.640%	$58.5023	$58.50	$58.50	$58.50
Purchase #4	$199.55	10.703%	$220.9078	$220.91	$220.90	$220.90
Purchase #5	$200.26	5.121%	$210.5153	$210.52	$210.50	$210.50
Purchase #6	$81.43	4.761%	$85.3069	$85.31	$85.30	$85.30
Purchase #7	$247.66	4.345%	$258.4208	$258.42	$258.40	$258.40
7 purchase totals =	$1,119.42		$1,209.3229	$1,209.33	$1,209.30	$1,209.30