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	$39.77	11.738%	$44.4382	$44.44	$44.45	$44.40
Purchase #2	$136.38	3.413%	$141.0346	$141.03	$141.05	$141.00
Purchase #3	$211.78	6.511%	$225.569	$225.57	$225.55	$225.60
Purchase #4	$59.46	9.497%	$65.1069	$65.11	$65.10	$65.10
Purchase #5	$102.25	8.653%	$111.0977	$111.10	$111.10	$111.10
Purchase #6	$223.92	10.865%	$248.2489	$248.25	$248.25	$248.20
Purchase #7	$36.90	7.167%	$39.5446	$39.54	$39.55	$39.50
7 purchase totals =	$810.46		$875.0399	$875.04	$875.05	$874.90