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	$43.99	3.582%	$45.5657	$45.57	$45.55	$45.60
Purchase #2	$64.88	12.672%	$73.1016	$73.10	$73.10	$73.10
Purchase #3	$86.36	11.290%	$96.11	$96.11	$96.10	$96.10
Purchase #4	$149.55	11.320%	$166.4791	$166.48	$166.50	$166.50
Purchase #5	$95.28	7.288%	$102.224	$102.22	$102.20	$102.20
Purchase #6	$100.35	11.167%	$111.5561	$111.56	$111.55	$111.60
Purchase #7	$138.59	6.344%	$147.3821	$147.38	$147.40	$147.40
7 purchase totals =	$679.00		$742.4186	$742.42	$742.40	$742.50