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	$155.74	10.280%	$171.7501	$171.75	$171.75	$171.80
Purchase #2	$168.44	13.244%	$190.7482	$190.75	$190.75	$190.70
Purchase #3	$214.39	4.259%	$223.5209	$223.52	$223.50	$223.50
Purchase #4	$85.96	8.289%	$93.0852	$93.09	$93.10	$93.10
Purchase #5	$82.36	9.690%	$90.3407	$90.34	$90.35	$90.30
Purchase #6	$42.60	6.518%	$45.3767	$45.38	$45.40	$45.40
Purchase #7	$119.71	11.803%	$133.8394	$133.84	$133.85	$133.80
7 purchase totals =	$869.20		$948.6612	$948.67	$948.70	$948.60