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	$154.83	10.465%	$171.033	$171.03	$171.05	$171.00
Purchase #2	$115.70	9.672%	$126.8905	$126.89	$126.90	$126.90
Purchase #3	$62.76	6.829%	$67.0459	$67.05	$67.05	$67.00
Purchase #4	$244.77	10.490%	$270.4464	$270.45	$270.45	$270.40
Purchase #5	$86.54	6.251%	$91.9496	$91.95	$91.95	$91.90
Purchase #6	$172.72	10.426%	$190.7278	$190.73	$190.75	$190.70
Purchase #7	$49.98	8.545%	$54.2508	$54.25	$54.25	$54.30
7 purchase totals =	$887.30		$972.3440	$972.35	$972.40	$972.20