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	$55.81	11.460%	$62.2058	$62.21	$62.20	$62.20
Purchase #2	$198.86	6.232%	$211.253	$211.25	$211.25	$211.30
Purchase #3	$169.95	9.387%	$185.9032	$185.90	$185.90	$185.90
Purchase #4	$65.46	3.128%	$67.5076	$67.51	$67.50	$67.50
Purchase #5	$37.25	10.279%	$41.0789	$41.08	$41.10	$41.10
Purchase #6	$96.76	3.147%	$99.805	$99.81	$99.80	$99.80
Purchase #7	$118.94	9.391%	$130.1097	$130.11	$130.10	$130.10
7 purchase totals =	$743.03		$797.8632	$797.87	$797.85	$797.90