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	$207.52	8.811%	$225.8046	$225.80	$225.80	$225.80
Purchase #2	$149.79	9.862%	$164.5623	$164.56	$164.55	$164.60
Purchase #3	$234.74	3.772%	$243.5944	$243.59	$243.60	$243.60
Purchase #4	$122.61	13.866%	$139.6111	$139.61	$139.60	$139.60
Purchase #5	$165.54	7.731%	$178.3379	$178.34	$178.35	$178.30
Purchase #6	$153.33	6.123%	$162.7184	$162.72	$162.70	$162.70
Purchase #7	$79.87	6.427%	$85.0032	$85.00	$85.00	$85.00
7 purchase totals =	$1,113.40		$1,199.6319	$1,199.62	$1,199.60	$1,199.60