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	$59.60	8.811%	$64.8514	$64.85	$64.85	$64.90
Purchase #2	$115.31	11.289%	$128.3273	$128.33	$128.35	$128.30
Purchase #3	$51.84	12.489%	$58.3143	$58.31	$58.30	$58.30
Purchase #4	$54.59	8.870%	$59.4321	$59.43	$59.45	$59.40
Purchase #5	$13.42	7.104%	$14.3734	$14.37	$14.35	$14.40
Purchase #6	$115.86	10.874%	$128.4586	$128.46	$128.45	$128.50
Purchase #7	$144.34	5.215%	$151.8673	$151.87	$151.85	$151.90
7 purchase totals =	$554.96		$605.6244	$605.62	$605.60	$605.70