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	$48.78	10.624%	$53.9624	$53.96	$53.95	$54.00
Purchase #2	$191.64	12.501%	$215.5969	$215.60	$215.60	$215.60
Purchase #3	$200.95	9.862%	$220.7677	$220.77	$220.75	$220.80
Purchase #4	$103.55	12.581%	$116.5776	$116.58	$116.60	$116.60
Purchase #5	$227.56	13.608%	$258.5264	$258.53	$258.55	$258.50
Purchase #6	$230.86	10.532%	$255.1742	$255.17	$255.15	$255.20
Purchase #7	$53.85	13.369%	$61.0492	$61.05	$61.05	$61.00
7 purchase totals =	$1,057.19		$1,181.6544	$1,181.66	$1,181.65	$1,181.70