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	$125.52	11.814%	$140.3489	$140.35	$140.35	$140.30
Purchase #2	$116.42	8.254%	$126.0293	$126.03	$126.05	$126.00
Purchase #3	$94.40	6.865%	$100.8806	$100.88	$100.90	$100.90
Purchase #4	$140.41	4.279%	$146.4181	$146.42	$146.40	$146.40
Purchase #5	$133.91	12.340%	$150.4345	$150.43	$150.45	$150.40
Purchase #6	$179.96	9.807%	$197.6087	$197.61	$197.60	$197.60
Purchase #7	$59.33	4.795%	$62.1749	$62.17	$62.15	$62.20
7 purchase totals =	$849.95		$923.8950	$923.89	$923.90	$923.80