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	$218.61	10.317%	$241.164	$241.16	$241.15	$241.20
Purchase #2	$117.90	9.692%	$129.3269	$129.33	$129.35	$129.30
Purchase #3	$7.72	5.300%	$8.1292	$8.13	$8.15	$8.10
Purchase #4	$42.78	8.697%	$46.5006	$46.50	$46.50	$46.50
Purchase #5	$70.72	10.829%	$78.3783	$78.38	$78.40	$78.40
Purchase #6	$89.55	8.119%	$96.8206	$96.82	$96.80	$96.80
Purchase #7	$157.65	6.244%	$167.4937	$167.49	$167.50	$167.50
7 purchase totals =	$704.93		$767.8133	$767.81	$767.85	$767.80