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	$114.79	11.306%	$127.7682	$127.77	$127.75	$127.80
Purchase #2	$92.57	4.698%	$96.9189	$96.92	$96.90	$96.90
Purchase #3	$110.92	9.870%	$121.8678	$121.87	$121.85	$121.90
Purchase #4	$54.33	4.780%	$56.927	$56.93	$56.95	$56.90
Purchase #5	$232.71	10.166%	$256.3673	$256.37	$256.35	$256.40
Purchase #6	$33.40	11.849%	$37.3576	$37.36	$37.35	$37.40
Purchase #7	$24.54	10.171%	$27.036	$27.04	$27.05	$27.00
7 purchase totals =	$663.26		$724.2428	$724.26	$724.20	$724.30