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	$104.44	9.849%	$114.7263	$114.73	$114.75	$114.70
Purchase #2	$178.98	7.184%	$191.8379	$191.84	$191.85	$191.80
Purchase #3	$144.40	5.138%	$151.8193	$151.82	$151.80	$151.80
Purchase #4	$92.79	8.497%	$100.6744	$100.67	$100.65	$100.70
Purchase #5	$86.43	6.234%	$91.818	$91.82	$91.80	$91.80
Purchase #6	$100.68	7.123%	$107.8514	$107.85	$107.85	$107.90
Purchase #7	$178.30	10.135%	$196.3707	$196.37	$196.35	$196.40
7 purchase totals =	$886.02		$955.0980	$955.10	$955.05	$955.10