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	$134.27	7.725%	$144.6424	$144.64	$144.65	$144.60
Purchase #2	$169.28	12.817%	$190.9766	$190.98	$191.00	$191.00
Purchase #3	$244.92	10.478%	$270.5827	$270.58	$270.60	$270.60
Purchase #4	$55.93	10.607%	$61.8625	$61.86	$61.85	$61.90
Purchase #5	$69.59	11.738%	$77.7585	$77.76	$77.75	$77.80
Purchase #6	$12.92	6.270%	$13.7301	$13.73	$13.75	$13.70
Purchase #7	$248.39	6.384%	$264.2472	$264.25	$264.25	$264.20
7 purchase totals =	$935.30		$1,023.8000	$1,023.80	$1,023.85	$1,023.80