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	$233.42	4.165%	$243.1419	$243.14	$243.15	$243.10
Purchase #2	$215.87	10.675%	$238.9141	$238.91	$238.90	$238.90
Purchase #3	$130.59	10.660%	$144.5109	$144.51	$144.50	$144.50
Purchase #4	$234.91	6.445%	$250.0499	$250.05	$250.05	$250.00
Purchase #5	$208.65	5.638%	$220.4137	$220.41	$220.40	$220.40
Purchase #6	$224.69	11.603%	$250.7608	$250.76	$250.75	$250.80
Purchase #7	$66.73	10.558%	$73.7754	$73.78	$73.80	$73.80
7 purchase totals =	$1,314.86		$1,421.5667	$1,421.56	$1,421.55	$1,421.50