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	$153.83	13.447%	$174.5155	$174.52	$174.50	$174.50
Purchase #2	$141.75	6.744%	$151.3096	$151.31	$151.30	$151.30
Purchase #3	$242.83	6.789%	$259.3157	$259.32	$259.30	$259.30
Purchase #4	$74.48	7.518%	$80.0794	$80.08	$80.10	$80.10
Purchase #5	$185.57	11.617%	$207.1277	$207.13	$207.15	$207.10
Purchase #6	$167.67	10.134%	$184.6617	$184.66	$184.65	$184.70
Purchase #7	$196.27	11.496%	$218.8332	$218.83	$218.85	$218.80
7 purchase totals =	$1,162.40		$1,275.8428	$1,275.85	$1,275.85	$1,275.80