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	$148.52	9.159%	$162.1229	$162.12	$162.10	$162.10
Purchase #2	$66.29	7.852%	$71.4951	$71.50	$71.50	$71.50
Purchase #3	$40.31	13.351%	$45.6918	$45.69	$45.70	$45.70
Purchase #4	$245.56	11.328%	$273.377	$273.38	$273.40	$273.40
Purchase #5	$39.73	8.324%	$43.0371	$43.04	$43.05	$43.00
Purchase #6	$78.71	5.277%	$82.8635	$82.86	$82.85	$82.90
Purchase #7	$70.46	7.417%	$75.686	$75.69	$75.70	$75.70
7 purchase totals =	$689.58		$754.2734	$754.28	$754.30	$754.30