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	$142.50	7.183%	$152.7358	$152.74	$152.75	$152.70
Purchase #2	$53.76	13.770%	$61.1628	$61.16	$61.15	$61.20
Purchase #3	$64.64	9.277%	$70.6367	$70.64	$70.65	$70.60
Purchase #4	$103.71	8.686%	$112.7183	$112.72	$112.70	$112.70
Purchase #5	$162.87	7.725%	$175.4517	$175.45	$175.45	$175.50
Purchase #6	$35.40	3.502%	$36.6397	$36.64	$36.65	$36.60
Purchase #7	$173.54	13.111%	$196.2928	$196.29	$196.30	$196.30
7 purchase totals =	$736.42		$805.6378	$805.64	$805.65	$805.60