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	$67.30	3.669%	$69.7692	$69.77	$69.75	$69.80
Purchase #2	$116.60	7.499%	$125.3438	$125.34	$125.35	$125.30
Purchase #3	$212.97	4.789%	$223.1691	$223.17	$223.15	$223.20
Purchase #4	$96.90	13.187%	$109.6782	$109.68	$109.70	$109.70
Purchase #5	$223.41	4.662%	$233.8254	$233.83	$233.85	$233.80
Purchase #6	$48.61	9.154%	$53.0598	$53.06	$53.05	$53.10
Purchase #7	$65.63	10.476%	$72.5054	$72.51	$72.50	$72.50
7 purchase totals =	$831.42		$887.3509	$887.36	$887.35	$887.40