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	$209.56	6.289%	$222.7392	$222.74	$222.75	$222.70
Purchase #2	$180.39	6.193%	$191.5616	$191.56	$191.55	$191.60
Purchase #3	$185.91	12.213%	$208.6152	$208.62	$208.60	$208.60
Purchase #4	$219.80	5.710%	$232.3506	$232.35	$232.35	$232.40
Purchase #5	$75.84	3.864%	$78.7705	$78.77	$78.75	$78.80
Purchase #6	$77.80	9.534%	$85.2175	$85.22	$85.20	$85.20
Purchase #7	$127.71	11.524%	$142.4273	$142.43	$142.45	$142.40
7 purchase totals =	$1,077.01		$1,161.6819	$1,161.69	$1,161.65	$1,161.70