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	$160.73	4.672%	$168.2393	$168.24	$168.25	$168.20
Purchase #2	$147.50	3.124%	$152.1079	$152.11	$152.10	$152.10
Purchase #3	$38.72	4.871%	$40.6061	$40.61	$40.60	$40.60
Purchase #4	$78.30	3.435%	$80.9896	$80.99	$81.00	$81.00
Purchase #5	$155.89	11.632%	$174.0231	$174.02	$174.00	$174.00
Purchase #6	$63.50	3.753%	$65.8832	$65.88	$65.90	$65.90
Purchase #7	$45.30	11.195%	$50.3713	$50.37	$50.35	$50.40
7 purchase totals =	$689.94		$732.2205	$732.22	$732.20	$732.20