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	$115.37	11.641%	$128.8002	$128.80	$128.80	$128.80
Purchase #2	$181.64	12.578%	$204.4867	$204.49	$204.50	$204.50
Purchase #3	$24.75	7.588%	$26.628	$26.63	$26.65	$26.60
Purchase #4	$72.61	5.512%	$76.6123	$76.61	$76.60	$76.60
Purchase #5	$136.64	10.183%	$150.5541	$150.55	$150.55	$150.60
Purchase #6	$187.60	11.601%	$209.3635	$209.36	$209.35	$209.40
Purchase #7	$239.29	10.690%	$264.8701	$264.87	$264.85	$264.90
7 purchase totals =	$957.90		$1,061.3149	$1,061.31	$1,061.30	$1,061.40