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	$82.90	13.553%	$94.1354	$94.14	$94.15	$94.10
Purchase #2	$23.72	4.646%	$24.822	$24.82	$24.80	$24.80
Purchase #3	$165.47	12.178%	$185.6209	$185.62	$185.60	$185.60
Purchase #4	$30.96	4.593%	$32.382	$32.38	$32.40	$32.40
Purchase #5	$168.67	13.305%	$191.1115	$191.11	$191.10	$191.10
Purchase #6	$163.27	7.118%	$174.8916	$174.89	$174.90	$174.90
Purchase #7	$178.49	5.360%	$188.0571	$188.06	$188.05	$188.10
7 purchase totals =	$813.48		$891.0205	$891.02	$891.00	$891.00