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	$98.59	11.335%	$109.7652	$109.77	$109.75	$109.80
Purchase #2	$5.47	11.660%	$6.1078	$6.11	$6.10	$6.10
Purchase #3	$90.35	9.618%	$99.0399	$99.04	$99.05	$99.00
Purchase #4	$38.95	3.118%	$40.1645	$40.16	$40.15	$40.20
Purchase #5	$174.78	9.629%	$191.6096	$191.61	$191.60	$191.60
Purchase #6	$170.71	7.701%	$183.8564	$183.86	$183.85	$183.90
Purchase #7	$93.93	4.557%	$98.2104	$98.21	$98.20	$98.20
7 purchase totals =	$672.78		$728.7538	$728.76	$728.70	$728.80