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	$95.29	4.725%	$99.7925	$99.79	$99.80	$99.80
Purchase #2	$100.69	9.615%	$110.3713	$110.37	$110.35	$110.40
Purchase #3	$78.32	10.142%	$86.2632	$86.26	$86.25	$86.30
Purchase #4	$159.93	5.438%	$168.627	$168.63	$168.65	$168.60
Purchase #5	$54.58	10.512%	$60.3174	$60.32	$60.30	$60.30
Purchase #6	$137.41	9.627%	$150.6385	$150.64	$150.65	$150.60
Purchase #7	$237.52	4.590%	$248.4222	$248.42	$248.40	$248.40
7 purchase totals =	$863.74		$924.4321	$924.43	$924.40	$924.40