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	$223.90	6.623%	$238.7289	$238.73	$238.75	$238.70
Purchase #2	$5.67	3.306%	$5.8575	$5.86	$5.85	$5.90
Purchase #3	$77.45	6.805%	$82.7205	$82.72	$82.70	$82.70
Purchase #4	$10.36	8.859%	$11.2778	$11.28	$11.30	$11.30
Purchase #5	$103.46	8.701%	$112.4621	$112.46	$112.45	$112.50
Purchase #6	$243.53	13.169%	$275.6005	$275.60	$275.60	$275.60
Purchase #7	$32.27	9.708%	$35.4028	$35.40	$35.40	$35.40
7 purchase totals =	$696.64		$762.0501	$762.05	$762.05	$762.10