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	$177.56	4.496%	$185.5431	$185.54	$185.55	$185.50
Purchase #2	$191.44	4.696%	$200.43	$200.43	$200.45	$200.40
Purchase #3	$150.74	6.270%	$160.1914	$160.19	$160.20	$160.20
Purchase #4	$106.96	10.523%	$118.2154	$118.22	$118.20	$118.20
Purchase #5	$138.29	12.152%	$155.095	$155.10	$155.10	$155.10
Purchase #6	$29.35	7.488%	$31.5477	$31.55	$31.55	$31.50
Purchase #7	$31.28	7.725%	$33.6964	$33.70	$33.70	$33.70
7 purchase totals =	$825.62		$884.7190	$884.73	$884.75	$884.60