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	$111.42	9.487%	$121.9904	$121.99	$122.00	$122.00
Purchase #2	$232.33	4.856%	$243.6119	$243.61	$243.60	$243.60
Purchase #3	$172.63	10.695%	$191.0928	$191.09	$191.10	$191.10
Purchase #4	$105.43	5.705%	$111.4448	$111.44	$111.45	$111.40
Purchase #5	$163.27	13.729%	$185.6853	$185.69	$185.70	$185.70
Purchase #6	$97.40	13.406%	$110.4574	$110.46	$110.45	$110.50
Purchase #7	$221.91	10.433%	$245.0619	$245.06	$245.05	$245.10
7 purchase totals =	$1,104.39		$1,209.3445	$1,209.34	$1,209.35	$1,209.40