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	$180.29	6.650%	$192.2793	$192.28	$192.30	$192.30
Purchase #2	$105.83	3.469%	$109.5012	$109.50	$109.50	$109.50
Purchase #3	$7.96	3.648%	$8.2504	$8.25	$8.25	$8.30
Purchase #4	$150.93	4.401%	$157.5724	$157.57	$157.55	$157.60
Purchase #5	$192.37	9.276%	$210.2142	$210.21	$210.20	$210.20
Purchase #6	$216.86	3.225%	$223.8537	$223.85	$223.85	$223.90
Purchase #7	$96.57	4.729%	$101.1368	$101.14	$101.15	$101.10
7 purchase totals =	$950.81		$1,002.8080	$1,002.80	$1,002.80	$1,002.90