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	$159.91	9.346%	$174.8552	$174.86	$174.85	$174.90
Purchase #2	$43.61	3.104%	$44.9637	$44.96	$44.95	$45.00
Purchase #3	$184.47	13.470%	$209.3181	$209.32	$209.30	$209.30
Purchase #4	$69.48	3.685%	$72.0403	$72.04	$72.05	$72.00
Purchase #5	$105.80	11.659%	$118.1352	$118.14	$118.15	$118.10
Purchase #6	$214.65	10.218%	$236.5829	$236.58	$236.60	$236.60
Purchase #7	$104.39	4.628%	$109.2212	$109.22	$109.20	$109.20
7 purchase totals =	$882.31		$965.1166	$965.12	$965.10	$965.10