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	$86.85	5.275%	$91.4313	$91.43	$91.45	$91.40
Purchase #2	$6.57	7.757%	$7.0796	$7.08	$7.10	$7.10
Purchase #3	$244.36	11.606%	$272.7204	$272.72	$272.70	$272.70
Purchase #4	$99.48	9.524%	$108.9545	$108.95	$108.95	$109.00
Purchase #5	$232.86	8.153%	$251.8451	$251.85	$251.85	$251.80
Purchase #6	$38.77	3.540%	$40.1425	$40.14	$40.15	$40.10
Purchase #7	$211.89	9.150%	$231.2779	$231.28	$231.30	$231.30
7 purchase totals =	$920.78		$1,003.4513	$1,003.45	$1,003.50	$1,003.40