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	$186.61	5.336%	$196.5675	$196.57	$196.55	$196.60
Purchase #2	$250.60	8.708%	$272.4222	$272.42	$272.40	$272.40
Purchase #3	$22.88	6.104%	$24.2766	$24.28	$24.30	$24.30
Purchase #4	$72.85	5.320%	$76.7256	$76.73	$76.75	$76.70
Purchase #5	$242.72	5.518%	$256.1133	$256.11	$256.10	$256.10
Purchase #6	$76.27	10.463%	$84.2501	$84.25	$84.25	$84.30
Purchase #7	$18.79	10.616%	$20.7847	$20.78	$20.80	$20.80
7 purchase totals =	$870.72		$931.1400	$931.14	$931.15	$931.20