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	$169.75	5.180%	$178.5431	$178.54	$178.55	$178.50
Purchase #2	$116.96	13.596%	$132.8619	$132.86	$132.85	$132.90
Purchase #3	$195.91	5.265%	$206.2247	$206.22	$206.20	$206.20
Purchase #4	$200.83	6.829%	$214.5447	$214.54	$214.55	$214.50
Purchase #5	$54.50	9.136%	$59.4791	$59.48	$59.50	$59.50
Purchase #6	$7.72	4.695%	$8.0825	$8.08	$8.10	$8.10
Purchase #7	$213.63	9.789%	$234.5422	$234.54	$234.55	$234.50
7 purchase totals =	$959.30		$1,034.2782	$1,034.26	$1,034.30	$1,034.20