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	$141.59	4.321%	$147.7081	$147.71	$147.70	$147.70
Purchase #2	$75.95	3.477%	$78.5908	$78.59	$78.60	$78.60
Purchase #3	$33.29	4.264%	$34.7095	$34.71	$34.70	$34.70
Purchase #4	$22.73	5.791%	$24.0463	$24.05	$24.05	$24.00
Purchase #5	$73.99	6.310%	$78.6588	$78.66	$78.65	$78.70
Purchase #6	$76.45	8.463%	$82.92	$82.92	$82.90	$82.90
Purchase #7	$89.39	7.532%	$96.1229	$96.12	$96.10	$96.10
7 purchase totals =	$513.39		$542.7564	$542.76	$542.70	$542.70