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	$224.64	6.144%	$238.4419	$238.44	$238.45	$238.40
Purchase #2	$176.34	8.746%	$191.7627	$191.76	$191.75	$191.80
Purchase #3	$64.99	11.341%	$72.3605	$72.36	$72.35	$72.40
Purchase #4	$55.73	12.472%	$62.6806	$62.68	$62.70	$62.70
Purchase #5	$247.48	7.600%	$266.2885	$266.29	$266.30	$266.30
Purchase #6	$37.82	12.236%	$42.4477	$42.45	$42.45	$42.40
Purchase #7	$204.59	12.813%	$230.8041	$230.80	$230.80	$230.80
7 purchase totals =	$1,011.59		$1,104.7860	$1,104.78	$1,104.80	$1,104.80