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	$144.46	13.510%	$163.9765	$163.98	$164.00	$164.00
Purchase #2	$54.76	11.518%	$61.0673	$61.07	$61.05	$61.10
Purchase #3	$88.98	12.667%	$100.2511	$100.25	$100.25	$100.30
Purchase #4	$119.69	9.332%	$130.8595	$130.86	$130.85	$130.90
Purchase #5	$47.84	10.241%	$52.7393	$52.74	$52.75	$52.70
Purchase #6	$72.45	10.591%	$80.1232	$80.12	$80.10	$80.10
Purchase #7	$57.61	7.192%	$61.7533	$61.75	$61.75	$61.80
7 purchase totals =	$585.79		$650.7702	$650.77	$650.75	$650.90