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	$98.31	12.836%	$110.9291	$110.93	$110.95	$110.90
Purchase #2	$148.84	13.429%	$168.8277	$168.83	$168.85	$168.80
Purchase #3	$134.51	7.463%	$144.5485	$144.55	$144.55	$144.50
Purchase #4	$33.79	9.845%	$37.1166	$37.12	$37.10	$37.10
Purchase #5	$215.66	9.523%	$236.1973	$236.20	$236.20	$236.20
Purchase #6	$141.49	7.782%	$152.5008	$152.50	$152.50	$152.50
Purchase #7	$86.28	7.261%	$92.5448	$92.54	$92.55	$92.50
7 purchase totals =	$858.88		$942.6648	$942.67	$942.70	$942.50