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	$27.53	12.815%	$31.058	$31.06	$31.05	$31.10
Purchase #2	$43.52	3.446%	$45.0197	$45.02	$45.00	$45.00
Purchase #3	$221.38	3.552%	$229.2434	$229.24	$229.25	$229.20
Purchase #4	$246.31	13.589%	$279.7811	$279.78	$279.80	$279.80
Purchase #5	$49.59	12.776%	$55.9256	$55.93	$55.95	$55.90
Purchase #6	$206.52	3.403%	$213.5479	$213.55	$213.55	$213.50
Purchase #7	$208.88	5.119%	$219.5726	$219.57	$219.55	$219.60
7 purchase totals =	$1,003.73		$1,074.1483	$1,074.15	$1,074.15	$1,074.10