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	$181.46	4.346%	$189.3463	$189.35	$189.35	$189.30
Purchase #2	$83.94	6.159%	$89.1099	$89.11	$89.10	$89.10
Purchase #3	$160.75	4.590%	$168.1284	$168.13	$168.15	$168.10
Purchase #4	$192.94	10.232%	$212.6816	$212.68	$212.70	$212.70
Purchase #5	$83.94	7.332%	$90.0945	$90.09	$90.10	$90.10
Purchase #6	$55.35	7.285%	$59.3822	$59.38	$59.40	$59.40
Purchase #7	$172.28	13.261%	$195.1261	$195.13	$195.15	$195.10
7 purchase totals =	$930.66		$1,003.8690	$1,003.87	$1,003.95	$1,003.80