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	$64.38	4.284%	$67.138	$67.14	$67.15	$67.10
Purchase #2	$59.28	10.213%	$65.3343	$65.33	$65.35	$65.30
Purchase #3	$95.32	7.166%	$102.1506	$102.15	$102.15	$102.20
Purchase #4	$240.56	3.510%	$249.0037	$249.00	$249.00	$249.00
Purchase #5	$25.39	12.833%	$28.6483	$28.65	$28.65	$28.60
Purchase #6	$64.56	3.353%	$66.7247	$66.72	$66.70	$66.70
Purchase #7	$86.82	6.467%	$92.4346	$92.43	$92.45	$92.40
7 purchase totals =	$636.31		$671.4342	$671.42	$671.45	$671.30