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	$92.92	13.124%	$105.1148	$105.11	$105.10	$105.10
Purchase #2	$223.87	6.465%	$238.3432	$238.34	$238.35	$238.30
Purchase #3	$92.41	10.175%	$101.8127	$101.81	$101.80	$101.80
Purchase #4	$219.43	5.630%	$231.7839	$231.78	$231.80	$231.80
Purchase #5	$71.53	13.667%	$81.306	$81.31	$81.30	$81.30
Purchase #6	$111.42	13.435%	$126.3893	$126.39	$126.40	$126.40
Purchase #7	$239.35	10.342%	$264.1036	$264.10	$264.10	$264.10
7 purchase totals =	$1,050.93		$1,148.8535	$1,148.84	$1,148.85	$1,148.80