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	$140.50	10.351%	$155.0432	$155.04	$155.05	$155.00
Purchase #2	$24.83	10.524%	$27.4431	$27.44	$27.45	$27.40
Purchase #3	$39.90	7.450%	$42.8726	$42.87	$42.85	$42.90
Purchase #4	$55.59	6.730%	$59.3312	$59.33	$59.35	$59.30
Purchase #5	$120.83	3.434%	$124.9793	$124.98	$125.00	$125.00
Purchase #6	$94.56	10.725%	$104.7016	$104.70	$104.70	$104.70
Purchase #7	$124.61	6.134%	$132.2536	$132.25	$132.25	$132.30
7 purchase totals =	$600.82		$646.6246	$646.61	$646.65	$646.60