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	$142.87	7.131%	$153.0581	$153.06	$153.05	$153.10
Purchase #2	$228.46	5.373%	$240.7352	$240.74	$240.75	$240.70
Purchase #3	$184.37	8.565%	$200.1613	$200.16	$200.15	$200.20
Purchase #4	$207.87	7.665%	$223.8032	$223.80	$223.80	$223.80
Purchase #5	$83.92	7.781%	$90.4498	$90.45	$90.45	$90.40
Purchase #6	$184.50	6.547%	$196.5792	$196.58	$196.60	$196.60
Purchase #7	$78.50	9.807%	$86.1985	$86.20	$86.20	$86.20
7 purchase totals =	$1,110.49		$1,190.9853	$1,190.99	$1,191.00	$1,191.00