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	$172.48	6.873%	$184.3346	$184.33	$184.35	$184.30
Purchase #2	$85.41	5.422%	$90.0409	$90.04	$90.05	$90.00
Purchase #3	$120.25	3.671%	$124.6644	$124.66	$124.65	$124.70
Purchase #4	$136.92	9.822%	$150.3683	$150.37	$150.35	$150.40
Purchase #5	$238.69	11.360%	$265.8052	$265.81	$265.80	$265.80
Purchase #6	$160.56	7.540%	$172.6662	$172.67	$172.65	$172.70
Purchase #7	$238.58	6.828%	$254.8702	$254.87	$254.85	$254.90
7 purchase totals =	$1,152.89		$1,242.7498	$1,242.75	$1,242.70	$1,242.80