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	$137.92	5.225%	$145.1263	$145.13	$145.15	$145.10
Purchase #2	$47.44	11.853%	$53.0631	$53.06	$53.05	$53.10
Purchase #3	$26.85	9.185%	$29.3162	$29.32	$29.30	$29.30
Purchase #4	$117.64	5.312%	$123.889	$123.89	$123.90	$123.90
Purchase #5	$164.90	11.645%	$184.1026	$184.10	$184.10	$184.10
Purchase #6	$189.86	5.776%	$200.8263	$200.83	$200.85	$200.80
Purchase #7	$103.40	7.556%	$111.2129	$111.21	$111.20	$111.20
7 purchase totals =	$788.01		$847.5364	$847.54	$847.55	$847.50