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	$209.35	9.268%	$228.7526	$228.75	$228.75	$228.80
Purchase #2	$53.61	11.839%	$59.9569	$59.96	$59.95	$60.00
Purchase #3	$31.89	5.274%	$33.5719	$33.57	$33.55	$33.60
Purchase #4	$200.79	5.450%	$211.7331	$211.73	$211.75	$211.70
Purchase #5	$12.67	13.210%	$14.3437	$14.34	$14.35	$14.30
Purchase #6	$93.83	13.438%	$106.4389	$106.44	$106.45	$106.40
Purchase #7	$45.90	11.245%	$51.0615	$51.06	$51.05	$51.10
7 purchase totals =	$648.04		$705.8586	$705.85	$705.85	$705.90