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	$98.50	4.415%	$102.8488	$102.85	$102.85	$102.80
Purchase #2	$71.40	10.337%	$78.7806	$78.78	$78.80	$78.80
Purchase #3	$184.77	11.386%	$205.8079	$205.81	$205.80	$205.80
Purchase #4	$203.40	3.415%	$210.3461	$210.35	$210.35	$210.30
Purchase #5	$93.62	7.738%	$100.8643	$100.86	$100.85	$100.90
Purchase #6	$218.29	5.786%	$230.9203	$230.92	$230.90	$230.90
Purchase #7	$26.61	6.506%	$28.3412	$28.34	$28.35	$28.30
7 purchase totals =	$896.59		$957.9092	$957.91	$957.90	$957.80