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	$115.83	6.268%	$123.0902	$123.09	$123.10	$123.10
Purchase #2	$32.33	7.489%	$34.7512	$34.75	$34.75	$34.80
Purchase #3	$175.60	7.585%	$188.9193	$188.92	$188.90	$188.90
Purchase #4	$207.34	13.482%	$235.2936	$235.29	$235.30	$235.30
Purchase #5	$32.41	13.406%	$36.7549	$36.75	$36.75	$36.80
Purchase #6	$242.45	13.646%	$275.5347	$275.53	$275.55	$275.50
Purchase #7	$176.41	11.599%	$196.8718	$196.87	$196.85	$196.90
7 purchase totals =	$982.37		$1,091.2157	$1,091.20	$1,091.20	$1,091.30