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	$62.30	10.641%	$68.9293	$68.93	$68.95	$68.90
Purchase #2	$175.77	11.743%	$196.4107	$196.41	$196.40	$196.40
Purchase #3	$248.66	6.316%	$264.3654	$264.37	$264.35	$264.40
Purchase #4	$195.73	8.839%	$213.0306	$213.03	$213.05	$213.00
Purchase #5	$220.45	12.709%	$248.467	$248.47	$248.45	$248.50
Purchase #6	$139.45	8.446%	$151.2279	$151.23	$151.25	$151.20
Purchase #7	$44.77	4.485%	$46.7779	$46.78	$46.80	$46.80
7 purchase totals =	$1,087.13		$1,189.2088	$1,189.22	$1,189.25	$1,189.20