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	$185.77	9.172%	$202.8088	$202.81	$202.80	$202.80
Purchase #2	$109.42	12.842%	$123.4717	$123.47	$123.45	$123.50
Purchase #3	$162.40	7.773%	$175.0234	$175.02	$175.00	$175.00
Purchase #4	$246.78	12.356%	$277.2721	$277.27	$277.25	$277.30
Purchase #5	$143.41	6.297%	$152.4405	$152.44	$152.45	$152.40
Purchase #6	$111.62	4.367%	$116.4944	$116.49	$116.50	$116.50
Purchase #7	$50.63	11.478%	$56.4413	$56.44	$56.45	$56.40
7 purchase totals =	$1,010.03		$1,103.9522	$1,103.94	$1,103.90	$1,103.90