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	$177.28	3.871%	$184.1425	$184.14	$184.15	$184.10
Purchase #2	$88.45	3.521%	$91.5643	$91.56	$91.55	$91.60
Purchase #3	$130.50	5.115%	$137.1751	$137.18	$137.20	$137.20
Purchase #4	$25.35	12.276%	$28.462	$28.46	$28.45	$28.50
Purchase #5	$31.87	5.697%	$33.6856	$33.69	$33.70	$33.70
Purchase #6	$83.34	7.217%	$89.3546	$89.35	$89.35	$89.40
Purchase #7	$103.48	6.397%	$110.0996	$110.10	$110.10	$110.10
7 purchase totals =	$640.27		$674.4837	$674.48	$674.50	$674.60