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	$145.46	3.121%	$149.9998	$150.00	$150.00	$150.00
Purchase #2	$50.26	12.682%	$56.634	$56.63	$56.65	$56.60
Purchase #3	$73.86	6.729%	$78.83	$78.83	$78.85	$78.80
Purchase #4	$109.78	13.107%	$124.1689	$124.17	$124.15	$124.20
Purchase #5	$186.58	12.798%	$210.4585	$210.46	$210.45	$210.50
Purchase #6	$197.63	13.161%	$223.6401	$223.64	$223.65	$223.60
Purchase #7	$55.97	7.162%	$59.9786	$59.98	$60.00	$60.00
7 purchase totals =	$819.54		$903.7099	$903.71	$903.75	$903.70