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	$136.32	7.294%	$146.2632	$146.26	$146.25	$146.30
Purchase #2	$226.75	3.470%	$234.6182	$234.62	$234.60	$234.60
Purchase #3	$85.62	6.417%	$91.1142	$91.11	$91.10	$91.10
Purchase #4	$226.33	7.110%	$242.4221	$242.42	$242.40	$242.40
Purchase #5	$28.97	11.739%	$32.3708	$32.37	$32.35	$32.40
Purchase #6	$233.84	6.236%	$248.4223	$248.42	$248.40	$248.40
Purchase #7	$69.52	4.740%	$72.8152	$72.82	$72.80	$72.80
7 purchase totals =	$1,007.35		$1,068.0260	$1,068.02	$1,067.90	$1,068.00