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	$171.88	12.822%	$193.9185	$193.92	$193.90	$193.90
Purchase #2	$174.47	9.712%	$191.4145	$191.41	$191.40	$191.40
Purchase #3	$164.35	10.607%	$181.7826	$181.78	$181.80	$181.80
Purchase #4	$90.83	9.735%	$99.6723	$99.67	$99.65	$99.70
Purchase #5	$81.82	4.153%	$85.218	$85.22	$85.20	$85.20
Purchase #6	$107.48	11.679%	$120.0326	$120.03	$120.05	$120.00
Purchase #7	$180.70	9.300%	$197.5051	$197.51	$197.50	$197.50
7 purchase totals =	$971.53		$1,069.5436	$1,069.54	$1,069.50	$1,069.50