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	$20.44	8.355%	$22.1478	$22.15	$22.15	$22.10
Purchase #2	$168.39	6.193%	$178.8184	$178.82	$178.80	$178.80
Purchase #3	$89.47	7.150%	$95.8671	$95.87	$95.85	$95.90
Purchase #4	$187.30	13.272%	$212.1585	$212.16	$212.15	$212.20
Purchase #5	$244.74	6.840%	$261.4802	$261.48	$261.50	$261.50
Purchase #6	$115.76	13.507%	$131.3957	$131.40	$131.40	$131.40
Purchase #7	$37.64	8.642%	$40.8928	$40.89	$40.90	$40.90
7 purchase totals =	$863.74		$942.7605	$942.77	$942.75	$942.80