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	$220.96	9.278%	$241.4607	$241.46	$241.45	$241.50
Purchase #2	$116.78	11.331%	$130.0123	$130.01	$130.00	$130.00
Purchase #3	$123.69	6.661%	$131.929	$131.93	$131.95	$131.90
Purchase #4	$151.26	9.300%	$165.3272	$165.33	$165.35	$165.30
Purchase #5	$37.97	12.114%	$42.5697	$42.57	$42.55	$42.60
Purchase #6	$55.36	12.793%	$62.4422	$62.44	$62.45	$62.40
Purchase #7	$99.74	9.795%	$109.5095	$109.51	$109.50	$109.50
7 purchase totals =	$805.76		$883.2506	$883.25	$883.25	$883.20