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	$85.76	7.516%	$92.2057	$92.21	$92.20	$92.20
Purchase #2	$201.74	10.764%	$223.4553	$223.46	$223.45	$223.50
Purchase #3	$147.53	11.809%	$164.9518	$164.95	$164.95	$165.00
Purchase #4	$100.46	4.323%	$104.8029	$104.80	$104.80	$104.80
Purchase #5	$152.93	3.828%	$158.7842	$158.78	$158.80	$158.80
Purchase #6	$155.30	5.799%	$164.3058	$164.31	$164.30	$164.30
Purchase #7	$141.77	7.503%	$152.407	$152.41	$152.40	$152.40
7 purchase totals =	$985.49		$1,060.9127	$1,060.92	$1,060.90	$1,061.00