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	$221.78	4.166%	$231.0194	$231.02	$231.00	$231.00
Purchase #2	$108.79	5.144%	$114.3862	$114.39	$114.40	$114.40
Purchase #3	$209.98	13.373%	$238.0606	$238.06	$238.05	$238.10
Purchase #4	$19.75	6.672%	$21.0677	$21.07	$21.05	$21.10
Purchase #5	$245.45	7.776%	$264.5362	$264.54	$264.55	$264.50
Purchase #6	$113.34	9.468%	$124.071	$124.07	$124.05	$124.10
Purchase #7	$47.96	11.655%	$53.5497	$53.55	$53.55	$53.50
7 purchase totals =	$967.05		$1,046.6908	$1,046.70	$1,046.65	$1,046.70