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	$96.98	11.466%	$108.0997	$108.10	$108.10	$108.10
Purchase #2	$38.33	9.616%	$42.0158	$42.02	$42.00	$42.00
Purchase #3	$69.32	7.574%	$74.5703	$74.57	$74.55	$74.60
Purchase #4	$169.42	7.800%	$182.6348	$182.63	$182.65	$182.60
Purchase #5	$117.37	11.566%	$130.945	$130.95	$130.95	$130.90
Purchase #6	$72.69	13.704%	$82.6514	$82.65	$82.65	$82.70
Purchase #7	$156.53	9.341%	$171.1515	$171.15	$171.15	$171.20
7 purchase totals =	$720.64		$792.0685	$792.07	$792.05	$792.10