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	$193.55	13.301%	$219.2941	$219.29	$219.30	$219.30
Purchase #2	$93.89	5.715%	$99.2558	$99.26	$99.25	$99.30
Purchase #3	$250.97	5.508%	$264.7934	$264.79	$264.80	$264.80
Purchase #4	$98.89	10.821%	$109.5909	$109.59	$109.60	$109.60
Purchase #5	$168.34	6.727%	$179.6642	$179.66	$179.65	$179.70
Purchase #6	$82.68	3.577%	$85.6375	$85.64	$85.65	$85.60
Purchase #7	$107.60	4.454%	$112.3925	$112.39	$112.40	$112.40
7 purchase totals =	$995.92		$1,070.6284	$1,070.62	$1,070.65	$1,070.70