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	$245.52	8.849%	$267.2461	$267.25	$267.25	$267.20
Purchase #2	$83.69	8.528%	$90.8271	$90.83	$90.85	$90.80
Purchase #3	$43.60	6.198%	$46.3023	$46.30	$46.30	$46.30
Purchase #4	$80.83	6.519%	$86.0993	$86.10	$86.10	$86.10
Purchase #5	$244.65	11.870%	$273.69	$273.69	$273.70	$273.70
Purchase #6	$135.82	8.664%	$147.5874	$147.59	$147.60	$147.60
Purchase #7	$190.56	11.666%	$212.7907	$212.79	$212.80	$212.80
7 purchase totals =	$1,024.67		$1,124.5429	$1,124.55	$1,124.60	$1,124.50