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	$35.27	7.371%	$37.8698	$37.87	$37.85	$37.90
Purchase #2	$192.87	6.649%	$205.6939	$205.69	$205.70	$205.70
Purchase #3	$72.91	13.240%	$82.5633	$82.56	$82.55	$82.60
Purchase #4	$62.94	13.555%	$71.4715	$71.47	$71.45	$71.50
Purchase #5	$119.53	4.122%	$124.457	$124.46	$124.45	$124.50
Purchase #6	$74.32	11.213%	$82.6535	$82.65	$82.65	$82.70
Purchase #7	$174.70	7.555%	$187.8986	$187.90	$187.90	$187.90
7 purchase totals =	$732.54		$792.6076	$792.60	$792.55	$792.80