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	$241.78	4.852%	$253.5112	$253.51	$253.50	$253.50
Purchase #2	$21.37	9.106%	$23.316	$23.32	$23.30	$23.30
Purchase #3	$140.64	7.747%	$151.5354	$151.54	$151.55	$151.50
Purchase #4	$101.89	11.456%	$113.5625	$113.56	$113.55	$113.60
Purchase #5	$134.65	9.568%	$147.5333	$147.53	$147.55	$147.50
Purchase #6	$209.68	9.293%	$229.1656	$229.17	$229.15	$229.20
Purchase #7	$89.34	8.422%	$96.8642	$96.86	$96.85	$96.90
7 purchase totals =	$939.35		$1,015.4882	$1,015.49	$1,015.45	$1,015.50