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	$207.46	7.604%	$223.2353	$223.24	$223.25	$223.20
Purchase #2	$189.97	5.560%	$200.5323	$200.53	$200.55	$200.50
Purchase #3	$43.82	11.141%	$48.702	$48.70	$48.70	$48.70
Purchase #4	$245.73	13.246%	$278.2794	$278.28	$278.30	$278.30
Purchase #5	$163.45	4.204%	$170.3214	$170.32	$170.30	$170.30
Purchase #6	$123.66	5.227%	$130.1237	$130.12	$130.10	$130.10
Purchase #7	$86.59	4.108%	$90.1471	$90.15	$90.15	$90.10
7 purchase totals =	$1,060.68		$1,141.3412	$1,141.34	$1,141.35	$1,141.20