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	$47.46	9.807%	$52.1144	$52.11	$52.10	$52.10
Purchase #2	$45.56	10.729%	$50.4481	$50.45	$50.45	$50.40
Purchase #3	$106.39	10.443%	$117.5003	$117.50	$117.50	$117.50
Purchase #4	$245.83	7.251%	$263.6551	$263.66	$263.65	$263.70
Purchase #5	$40.79	4.754%	$42.7292	$42.73	$42.75	$42.70
Purchase #6	$27.33	5.751%	$28.9017	$28.90	$28.90	$28.90
Purchase #7	$67.72	13.791%	$77.0593	$77.06	$77.05	$77.10
7 purchase totals =	$581.08		$632.4081	$632.41	$632.40	$632.40