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	$168.29	3.834%	$174.7422	$174.74	$174.75	$174.70
Purchase #2	$94.45	9.226%	$103.164	$103.16	$103.15	$103.20
Purchase #3	$53.55	12.662%	$60.3305	$60.33	$60.35	$60.30
Purchase #4	$241.77	12.451%	$271.8728	$271.87	$271.85	$271.90
Purchase #5	$141.71	11.417%	$157.889	$157.89	$157.90	$157.90
Purchase #6	$109.57	12.776%	$123.5687	$123.57	$123.55	$123.60
Purchase #7	$127.74	5.166%	$134.339	$134.34	$134.35	$134.30
7 purchase totals =	$937.08		$1,025.9062	$1,025.90	$1,025.90	$1,025.90