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	$130.40	7.830%	$140.6103	$140.61	$140.60	$140.60
Purchase #2	$52.40	4.706%	$54.8659	$54.87	$54.85	$54.90
Purchase #3	$91.87	4.684%	$96.1732	$96.17	$96.15	$96.20
Purchase #4	$53.79	7.379%	$57.7592	$57.76	$57.75	$57.80
Purchase #5	$224.38	9.432%	$245.5435	$245.54	$245.55	$245.50
Purchase #6	$124.29	4.675%	$130.1006	$130.10	$130.10	$130.10
Purchase #7	$40.25	3.325%	$41.5883	$41.59	$41.60	$41.60
7 purchase totals =	$717.38		$766.6410	$766.64	$766.60	$766.70