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	$174.51	3.590%	$180.7749	$180.77	$180.75	$180.80
Purchase #2	$64.82	9.538%	$71.0025	$71.00	$71.00	$71.00
Purchase #3	$82.93	7.389%	$89.0577	$89.06	$89.05	$89.10
Purchase #4	$43.30	10.530%	$47.8595	$47.86	$47.85	$47.90
Purchase #5	$75.99	9.234%	$83.0069	$83.01	$83.00	$83.00
Purchase #6	$190.68	10.424%	$210.5565	$210.56	$210.55	$210.60
Purchase #7	$40.75	13.572%	$46.2806	$46.28	$46.30	$46.30
7 purchase totals =	$672.98		$728.5386	$728.54	$728.50	$728.70