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	$146.34	4.292%	$152.6209	$152.62	$152.60	$152.60
Purchase #2	$246.90	3.298%	$255.0428	$255.04	$255.05	$255.00
Purchase #3	$232.52	13.302%	$263.4498	$263.45	$263.45	$263.40
Purchase #4	$227.38	3.246%	$234.7608	$234.76	$234.75	$234.80
Purchase #5	$116.33	9.406%	$127.272	$127.27	$127.25	$127.30
Purchase #6	$86.56	13.405%	$98.1634	$98.16	$98.15	$98.20
Purchase #7	$113.98	3.400%	$117.8553	$117.86	$117.85	$117.90
7 purchase totals =	$1,170.01		$1,249.1650	$1,249.16	$1,249.10	$1,249.20