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	$168.69	12.204%	$189.2769	$189.28	$189.30	$189.30
Purchase #2	$168.39	6.632%	$179.5576	$179.56	$179.55	$179.60
Purchase #3	$118.89	3.647%	$123.2259	$123.23	$123.25	$123.20
Purchase #4	$170.79	8.605%	$185.4865	$185.49	$185.50	$185.50
Purchase #5	$123.54	12.320%	$138.7601	$138.76	$138.75	$138.80
Purchase #6	$174.96	13.245%	$198.1335	$198.13	$198.15	$198.10
Purchase #7	$8.55	11.353%	$9.5207	$9.52	$9.50	$9.50
7 purchase totals =	$933.81		$1,023.9612	$1,023.97	$1,024.00	$1,024.00