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	$196.38	11.717%	$219.3898	$219.39	$219.40	$219.40
Purchase #2	$24.93	11.572%	$27.8149	$27.81	$27.80	$27.80
Purchase #3	$191.73	6.707%	$204.5893	$204.59	$204.60	$204.60
Purchase #4	$75.30	3.361%	$77.8308	$77.83	$77.85	$77.80
Purchase #5	$240.73	10.421%	$265.8165	$265.82	$265.80	$265.80
Purchase #6	$42.85	6.541%	$45.6528	$45.65	$45.65	$45.70
Purchase #7	$248.73	12.520%	$279.871	$279.87	$279.85	$279.90
7 purchase totals =	$1,020.65		$1,120.9651	$1,120.96	$1,120.95	$1,121.00