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	$194.72	4.566%	$203.6109	$203.61	$203.60	$203.60
Purchase #2	$76.47	7.285%	$82.0408	$82.04	$82.05	$82.00
Purchase #3	$85.61	13.662%	$97.306	$97.31	$97.30	$97.30
Purchase #4	$244.85	10.382%	$270.2703	$270.27	$270.25	$270.30
Purchase #5	$162.25	11.228%	$180.4674	$180.47	$180.45	$180.50
Purchase #6	$43.82	4.207%	$45.6635	$45.66	$45.65	$45.70
Purchase #7	$195.40	13.822%	$222.4082	$222.41	$222.40	$222.40
7 purchase totals =	$1,003.12		$1,101.7671	$1,101.77	$1,101.70	$1,101.80