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	$122.44	4.183%	$127.5617	$127.56	$127.55	$127.60
Purchase #2	$141.74	8.394%	$153.6377	$153.64	$153.65	$153.60
Purchase #3	$112.98	6.452%	$120.2695	$120.27	$120.25	$120.30
Purchase #4	$182.65	7.648%	$196.6191	$196.62	$196.60	$196.60
Purchase #5	$210.36	5.799%	$222.5588	$222.56	$222.55	$222.60
Purchase #6	$139.60	10.503%	$154.2622	$154.26	$154.25	$154.30
Purchase #7	$69.49	3.862%	$72.1737	$72.17	$72.15	$72.20
7 purchase totals =	$979.26		$1,047.0827	$1,047.08	$1,047.00	$1,047.20