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	$174.69	4.675%	$182.8568	$182.86	$182.85	$182.90
Purchase #2	$117.93	9.267%	$128.8586	$128.86	$128.85	$128.90
Purchase #3	$54.93	11.323%	$61.1497	$61.15	$61.15	$61.10
Purchase #4	$155.40	4.360%	$162.1754	$162.18	$162.20	$162.20
Purchase #5	$151.69	10.285%	$167.2913	$167.29	$167.30	$167.30
Purchase #6	$60.47	9.711%	$66.3422	$66.34	$66.35	$66.30
Purchase #7	$245.39	13.377%	$278.2158	$278.22	$278.20	$278.20
7 purchase totals =	$960.50		$1,046.8898	$1,046.90	$1,046.90	$1,046.90