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	$132.91	10.798%	$147.2616	$147.26	$147.25	$147.30
Purchase #2	$96.89	5.191%	$101.9196	$101.92	$101.90	$101.90
Purchase #3	$201.89	6.333%	$214.6757	$214.68	$214.70	$214.70
Purchase #4	$249.43	3.682%	$258.614	$258.61	$258.60	$258.60
Purchase #5	$178.58	6.666%	$190.4841	$190.48	$190.50	$190.50
Purchase #6	$91.89	8.383%	$99.5931	$99.59	$99.60	$99.60
Purchase #7	$37.33	5.403%	$39.3469	$39.35	$39.35	$39.30
7 purchase totals =	$988.92		$1,051.8950	$1,051.89	$1,051.90	$1,051.90