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	$169.94	12.336%	$190.9038	$190.90	$190.90	$190.90
Purchase #2	$188.39	6.227%	$200.121	$200.12	$200.10	$200.10
Purchase #3	$7.94	4.274%	$8.2794	$8.28	$8.30	$8.30
Purchase #4	$88.61	13.774%	$100.8151	$100.82	$100.80	$100.80
Purchase #5	$120.96	3.736%	$125.4791	$125.48	$125.50	$125.50
Purchase #6	$225.35	3.423%	$233.0637	$233.06	$233.05	$233.10
Purchase #7	$139.76	5.611%	$147.6019	$147.60	$147.60	$147.60
7 purchase totals =	$940.95		$1,006.2640	$1,006.26	$1,006.25	$1,006.30