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	$182.64	9.587%	$200.1497	$200.15	$200.15	$200.10
Purchase #2	$50.59	9.281%	$55.2853	$55.29	$55.30	$55.30
Purchase #3	$239.78	12.320%	$269.3209	$269.32	$269.30	$269.30
Purchase #4	$220.59	11.594%	$246.1652	$246.17	$246.15	$246.20
Purchase #5	$84.41	5.258%	$88.8483	$88.85	$88.85	$88.80
Purchase #6	$21.27	7.400%	$22.844	$22.84	$22.85	$22.80
Purchase #7	$172.27	7.505%	$185.1989	$185.20	$185.20	$185.20
7 purchase totals =	$971.55		$1,067.8123	$1,067.82	$1,067.80	$1,067.70