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	$158.35	4.731%	$165.8415	$165.84	$165.85	$165.80
Purchase #2	$59.47	5.746%	$62.8871	$62.89	$62.90	$62.90
Purchase #3	$234.80	3.428%	$242.8489	$242.85	$242.85	$242.80
Purchase #4	$33.80	8.860%	$36.7947	$36.79	$36.80	$36.80
Purchase #5	$32.31	9.398%	$35.3465	$35.35	$35.35	$35.30
Purchase #6	$21.40	5.285%	$22.531	$22.53	$22.55	$22.50
Purchase #7	$40.33	7.714%	$43.4411	$43.44	$43.45	$43.40
7 purchase totals =	$580.46		$609.6908	$609.69	$609.75	$609.50