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	$143.56	6.171%	$152.4191	$152.42	$152.40	$152.40
Purchase #2	$185.35	10.565%	$204.9322	$204.93	$204.95	$204.90
Purchase #3	$240.77	11.450%	$268.3382	$268.34	$268.35	$268.30
Purchase #4	$130.94	9.434%	$143.2929	$143.29	$143.30	$143.30
Purchase #5	$136.38	7.457%	$146.5499	$146.55	$146.55	$146.50
Purchase #6	$37.96	11.677%	$42.3926	$42.39	$42.40	$42.40
Purchase #7	$128.46	11.528%	$143.2689	$143.27	$143.25	$143.30
7 purchase totals =	$1,003.42		$1,101.1938	$1,101.19	$1,101.20	$1,101.10