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	$38.61	11.686%	$43.122	$43.12	$43.10	$43.10
Purchase #2	$130.33	12.145%	$146.1586	$146.16	$146.15	$146.20
Purchase #3	$21.50	13.529%	$24.4087	$24.41	$24.40	$24.40
Purchase #4	$83.54	7.464%	$89.7754	$89.78	$89.80	$89.80
Purchase #5	$44.52	5.710%	$47.0621	$47.06	$47.05	$47.10
Purchase #6	$186.30	12.394%	$209.39	$209.39	$209.40	$209.40
Purchase #7	$155.54	9.292%	$169.9928	$169.99	$170.00	$170.00
7 purchase totals =	$660.34		$729.9096	$729.91	$729.90	$730.00