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	$162.40	13.440%	$184.2266	$184.23	$184.25	$184.20
Purchase #2	$76.45	3.237%	$78.9247	$78.92	$78.90	$78.90
Purchase #3	$137.56	12.226%	$154.3781	$154.38	$154.40	$154.40
Purchase #4	$161.37	3.763%	$167.4424	$167.44	$167.45	$167.40
Purchase #5	$240.45	9.865%	$264.1704	$264.17	$264.15	$264.20
Purchase #6	$14.29	3.592%	$14.8033	$14.80	$14.80	$14.80
Purchase #7	$35.46	13.587%	$40.278	$40.28	$40.30	$40.30
7 purchase totals =	$827.98		$904.2235	$904.22	$904.25	$904.20