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	$94.38	5.478%	$99.5501	$99.55	$99.55	$99.60
Purchase #2	$193.74	7.231%	$207.7493	$207.75	$207.75	$207.70
Purchase #3	$228.36	11.768%	$255.2334	$255.23	$255.25	$255.20
Purchase #4	$56.91	8.361%	$61.6682	$61.67	$61.65	$61.70
Purchase #5	$123.47	6.472%	$131.461	$131.46	$131.45	$131.50
Purchase #6	$213.89	11.380%	$238.2307	$238.23	$238.25	$238.20
Purchase #7	$27.38	8.138%	$29.6082	$29.61	$29.60	$29.60
7 purchase totals =	$938.13		$1,023.5009	$1,023.50	$1,023.50	$1,023.50