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	$128.32	13.645%	$145.8293	$145.83	$145.85	$145.80
Purchase #2	$168.64	11.860%	$188.6407	$188.64	$188.65	$188.60
Purchase #3	$134.27	6.179%	$142.5665	$142.57	$142.55	$142.60
Purchase #4	$239.72	13.536%	$272.1685	$272.17	$272.15	$272.20
Purchase #5	$161.98	13.648%	$184.087	$184.09	$184.10	$184.10
Purchase #6	$145.61	4.490%	$152.1479	$152.15	$152.15	$152.10
Purchase #7	$220.56	12.327%	$247.7484	$247.75	$247.75	$247.70
7 purchase totals =	$1,199.10		$1,333.1883	$1,333.20	$1,333.20	$1,333.10