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	$120.63	10.859%	$133.7292	$133.73	$133.75	$133.70
Purchase #2	$100.83	4.699%	$105.568	$105.57	$105.55	$105.60
Purchase #3	$242.39	12.676%	$273.1154	$273.12	$273.10	$273.10
Purchase #4	$55.43	6.436%	$58.9975	$59.00	$59.00	$59.00
Purchase #5	$165.79	13.566%	$188.2811	$188.28	$188.30	$188.30
Purchase #6	$224.49	10.346%	$247.7157	$247.72	$247.70	$247.70
Purchase #7	$244.67	11.569%	$272.9759	$272.98	$273.00	$273.00
7 purchase totals =	$1,154.23		$1,280.3828	$1,280.40	$1,280.40	$1,280.40