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	$96.69	7.451%	$103.8944	$103.89	$103.90	$103.90
Purchase #2	$198.79	12.322%	$223.2849	$223.28	$223.30	$223.30
Purchase #3	$167.35	13.255%	$189.5322	$189.53	$189.55	$189.50
Purchase #4	$172.77	7.616%	$185.9282	$185.93	$185.95	$185.90
Purchase #5	$174.35	3.317%	$180.1332	$180.13	$180.15	$180.10
Purchase #6	$148.98	10.106%	$164.0359	$164.04	$164.05	$164.00
Purchase #7	$15.54	8.453%	$16.8536	$16.85	$16.85	$16.90
7 purchase totals =	$974.47		$1,063.6624	$1,063.65	$1,063.75	$1,063.60