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	$174.57	9.378%	$190.9412	$190.94	$190.95	$190.90
Purchase #2	$85.72	11.142%	$95.2709	$95.27	$95.25	$95.30
Purchase #3	$215.80	5.264%	$227.1597	$227.16	$227.15	$227.20
Purchase #4	$197.60	10.356%	$218.0635	$218.06	$218.05	$218.10
Purchase #5	$136.66	8.200%	$147.8661	$147.87	$147.85	$147.90
Purchase #6	$25.60	11.251%	$28.4803	$28.48	$28.50	$28.50
Purchase #7	$117.52	8.736%	$127.7865	$127.79	$127.80	$127.80
7 purchase totals =	$953.47		$1,035.5682	$1,035.57	$1,035.55	$1,035.70