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	$61.65	7.303%	$66.1523	$66.15	$66.15	$66.20
Purchase #2	$6.48	12.743%	$7.3057	$7.31	$7.30	$7.30
Purchase #3	$141.77	13.312%	$160.6424	$160.64	$160.65	$160.60
Purchase #4	$147.86	13.613%	$167.9882	$167.99	$168.00	$168.00
Purchase #5	$150.53	13.746%	$171.2219	$171.22	$171.20	$171.20
Purchase #6	$85.60	4.173%	$89.1721	$89.17	$89.15	$89.20
Purchase #7	$28.76	10.481%	$31.7743	$31.77	$31.75	$31.80
7 purchase totals =	$622.65		$694.2569	$694.25	$694.20	$694.30