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	$207.27	10.545%	$229.1266	$229.13	$229.15	$229.10
Purchase #2	$75.69	7.647%	$81.478	$81.48	$81.50	$81.50
Purchase #3	$147.83	5.536%	$156.0139	$156.01	$156.00	$156.00
Purchase #4	$222.57	10.139%	$245.1364	$245.14	$245.15	$245.10
Purchase #5	$244.60	13.550%	$277.7433	$277.74	$277.75	$277.70
Purchase #6	$88.46	13.515%	$100.4154	$100.42	$100.40	$100.40
Purchase #7	$170.87	8.509%	$185.4093	$185.41	$185.40	$185.40
7 purchase totals =	$1,157.29		$1,275.3229	$1,275.33	$1,275.35	$1,275.20