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	$186.32	13.330%	$211.1565	$211.16	$211.15	$211.20
Purchase #2	$81.80	13.441%	$92.7947	$92.79	$92.80	$92.80
Purchase #3	$195.34	13.743%	$222.1856	$222.19	$222.20	$222.20
Purchase #4	$203.75	3.326%	$210.5267	$210.53	$210.55	$210.50
Purchase #5	$11.29	10.577%	$12.4841	$12.48	$12.50	$12.50
Purchase #6	$223.38	6.326%	$237.511	$237.51	$237.50	$237.50
Purchase #7	$72.60	12.256%	$81.4979	$81.50	$81.50	$81.50
7 purchase totals =	$974.48		$1,068.1565	$1,068.16	$1,068.20	$1,068.20