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	$56.37	5.126%	$59.2595	$59.26	$59.25	$59.30
Purchase #2	$92.83	13.800%	$105.6405	$105.64	$105.65	$105.60
Purchase #3	$88.90	8.306%	$96.284	$96.28	$96.30	$96.30
Purchase #4	$234.78	4.257%	$244.7746	$244.77	$244.75	$244.80
Purchase #5	$77.69	13.535%	$88.2053	$88.21	$88.20	$88.20
Purchase #6	$131.87	7.633%	$141.9356	$141.94	$141.95	$141.90
Purchase #7	$222.39	12.543%	$250.2844	$250.28	$250.30	$250.30
7 purchase totals =	$904.83		$986.3839	$986.38	$986.40	$986.40