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	$142.35	4.256%	$148.4084	$148.41	$148.40	$148.40
Purchase #2	$72.49	11.267%	$80.6574	$80.66	$80.65	$80.70
Purchase #3	$77.64	12.407%	$87.2728	$87.27	$87.25	$87.30
Purchase #4	$225.73	7.786%	$243.3053	$243.31	$243.30	$243.30
Purchase #5	$89.30	11.405%	$99.4847	$99.48	$99.50	$99.50
Purchase #6	$125.59	5.559%	$132.5715	$132.57	$132.55	$132.60
Purchase #7	$229.61	9.371%	$251.1268	$251.13	$251.15	$251.10
7 purchase totals =	$962.71		$1,042.8269	$1,042.83	$1,042.80	$1,042.90