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	$126.56	3.800%	$131.3693	$131.37	$131.35	$131.40
Purchase #2	$32.74	11.566%	$36.5267	$36.53	$36.55	$36.50
Purchase #3	$183.71	11.304%	$204.4766	$204.48	$204.50	$204.50
Purchase #4	$168.32	13.487%	$191.0213	$191.02	$191.00	$191.00
Purchase #5	$115.81	7.193%	$124.1402	$124.14	$124.15	$124.10
Purchase #6	$179.48	7.107%	$192.2356	$192.24	$192.25	$192.20
Purchase #7	$243.94	11.599%	$272.2346	$272.23	$272.25	$272.20
7 purchase totals =	$1,050.56		$1,152.0043	$1,152.01	$1,152.05	$1,151.90