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	$190.59	4.248%	$198.6863	$198.69	$198.70	$198.70
Purchase #2	$201.73	6.492%	$214.8263	$214.83	$214.85	$214.80
Purchase #3	$96.28	9.504%	$105.4305	$105.43	$105.45	$105.40
Purchase #4	$109.81	8.250%	$118.8693	$118.87	$118.85	$118.90
Purchase #5	$133.35	10.579%	$147.4571	$147.46	$147.45	$147.50
Purchase #6	$28.74	12.817%	$32.4236	$32.42	$32.40	$32.40
Purchase #7	$223.99	8.234%	$242.4333	$242.43	$242.45	$242.40
7 purchase totals =	$984.49		$1,060.1264	$1,060.13	$1,060.15	$1,060.10