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	$114.42	12.669%	$128.9159	$128.92	$128.90	$128.90
Purchase #2	$233.31	13.131%	$263.9459	$263.95	$263.95	$263.90
Purchase #3	$147.97	7.159%	$158.5632	$158.56	$158.55	$158.60
Purchase #4	$246.47	5.450%	$259.9026	$259.90	$259.90	$259.90
Purchase #5	$18.98	12.243%	$21.3037	$21.30	$21.30	$21.30
Purchase #6	$31.95	12.250%	$35.8639	$35.86	$35.85	$35.90
Purchase #7	$207.48	4.427%	$216.6651	$216.67	$216.65	$216.70
7 purchase totals =	$1,000.58		$1,085.1603	$1,085.16	$1,085.10	$1,085.20