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	$151.86	10.516%	$167.8296	$167.83	$167.85	$167.80
Purchase #2	$209.70	4.395%	$218.9163	$218.92	$218.90	$218.90
Purchase #3	$46.25	7.600%	$49.765	$49.77	$49.75	$49.80
Purchase #4	$17.89	8.304%	$19.3756	$19.38	$19.40	$19.40
Purchase #5	$143.32	10.712%	$158.6724	$158.67	$158.65	$158.70
Purchase #6	$146.41	11.123%	$162.6952	$162.70	$162.70	$162.70
Purchase #7	$54.63	12.198%	$61.2938	$61.29	$61.30	$61.30
7 purchase totals =	$770.06		$838.5479	$838.56	$838.55	$838.60