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	$166.41	7.599%	$179.0555	$179.06	$179.05	$179.10
Purchase #2	$244.30	12.472%	$274.7691	$274.77	$274.75	$274.80
Purchase #3	$179.83	7.460%	$193.2453	$193.25	$193.25	$193.20
Purchase #4	$78.40	13.227%	$88.77	$88.77	$88.75	$88.80
Purchase #5	$168.67	5.759%	$178.3837	$178.38	$178.40	$178.40
Purchase #6	$98.45	6.541%	$104.8896	$104.89	$104.90	$104.90
Purchase #7	$173.47	10.428%	$191.5595	$191.56	$191.55	$191.60
7 purchase totals =	$1,109.53		$1,210.6727	$1,210.68	$1,210.65	$1,210.80