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	$193.25	10.483%	$213.5084	$213.51	$213.50	$213.50
Purchase #2	$37.89	10.265%	$41.7794	$41.78	$41.80	$41.80
Purchase #3	$216.70	6.284%	$230.3174	$230.32	$230.30	$230.30
Purchase #4	$81.73	9.841%	$89.773	$89.77	$89.75	$89.80
Purchase #5	$197.41	4.451%	$206.1967	$206.20	$206.20	$206.20
Purchase #6	$228.79	3.779%	$237.436	$237.44	$237.45	$237.40
Purchase #7	$104.54	4.138%	$108.8659	$108.87	$108.85	$108.90
7 purchase totals =	$1,060.31		$1,127.8768	$1,127.89	$1,127.85	$1,127.90