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	$237.85	9.181%	$259.687	$259.69	$259.70	$259.70
Purchase #2	$165.72	12.268%	$186.0505	$186.05	$186.05	$186.10
Purchase #3	$49.64	7.790%	$53.507	$53.51	$53.50	$53.50
Purchase #4	$89.85	3.422%	$92.9247	$92.92	$92.90	$92.90
Purchase #5	$90.74	10.468%	$100.2387	$100.24	$100.25	$100.20
Purchase #6	$16.30	7.103%	$17.4578	$17.46	$17.45	$17.50
Purchase #7	$174.28	11.587%	$194.4738	$194.47	$194.45	$194.50
7 purchase totals =	$824.38		$904.3395	$904.34	$904.30	$904.40