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	$81.51	13.242%	$92.3036	$92.30	$92.30	$92.30
Purchase #2	$63.27	13.687%	$71.9298	$71.93	$71.95	$71.90
Purchase #3	$126.45	10.574%	$139.8208	$139.82	$139.80	$139.80
Purchase #4	$61.55	10.344%	$67.9167	$67.92	$67.90	$67.90
Purchase #5	$249.27	3.200%	$257.2466	$257.25	$257.25	$257.20
Purchase #6	$218.69	10.442%	$241.5256	$241.53	$241.55	$241.50
Purchase #7	$140.57	4.573%	$146.9983	$147.00	$147.00	$147.00
7 purchase totals =	$941.31		$1,017.7414	$1,017.75	$1,017.75	$1,017.60