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	$213.32	5.666%	$225.4067	$225.41	$225.40	$225.40
Purchase #2	$243.40	12.765%	$274.47	$274.47	$274.45	$274.50
Purchase #3	$40.38	11.386%	$44.9777	$44.98	$45.00	$45.00
Purchase #4	$119.65	6.651%	$127.6079	$127.61	$127.60	$127.60
Purchase #5	$26.83	11.810%	$29.9986	$30.00	$30.00	$30.00
Purchase #6	$211.97	5.289%	$223.1811	$223.18	$223.20	$223.20
Purchase #7	$207.30	6.760%	$221.3135	$221.31	$221.30	$221.30
7 purchase totals =	$1,062.85		$1,146.9555	$1,146.96	$1,146.95	$1,147.00