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	$168.62	13.283%	$191.0178	$191.02	$191.00	$191.00
Purchase #2	$241.74	11.241%	$268.914	$268.91	$268.90	$268.90
Purchase #3	$129.73	3.645%	$134.4587	$134.46	$134.45	$134.50
Purchase #4	$24.56	11.211%	$27.3134	$27.31	$27.30	$27.30
Purchase #5	$55.85	8.831%	$60.7821	$60.78	$60.80	$60.80
Purchase #6	$247.29	4.698%	$258.9077	$258.91	$258.90	$258.90
Purchase #7	$31.53	7.505%	$33.8963	$33.90	$33.90	$33.90
7 purchase totals =	$899.32		$975.2900	$975.29	$975.25	$975.30