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	$37.26	11.174%	$41.4234	$41.42	$41.40	$41.40
Purchase #2	$177.77	11.694%	$198.5584	$198.56	$198.55	$198.60
Purchase #3	$218.80	4.793%	$229.2871	$229.29	$229.30	$229.30
Purchase #4	$59.30	8.346%	$64.2492	$64.25	$64.25	$64.20
Purchase #5	$122.25	6.539%	$130.2439	$130.24	$130.25	$130.20
Purchase #6	$240.31	10.594%	$265.7684	$265.77	$265.75	$265.80
Purchase #7	$143.70	9.109%	$156.7896	$156.79	$156.80	$156.80
7 purchase totals =	$999.39		$1,086.3200	$1,086.32	$1,086.30	$1,086.30