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	$212.33	10.114%	$233.8051	$233.81	$233.80	$233.80
Purchase #2	$94.66	11.857%	$105.8838	$105.88	$105.90	$105.90
Purchase #3	$45.34	5.115%	$47.6591	$47.66	$47.65	$47.70
Purchase #4	$181.59	13.288%	$205.7197	$205.72	$205.70	$205.70
Purchase #5	$161.30	7.154%	$172.8394	$172.84	$172.85	$172.80
Purchase #6	$61.92	5.582%	$65.3764	$65.38	$65.40	$65.40
Purchase #7	$196.43	8.195%	$212.5274	$212.53	$212.55	$212.50
7 purchase totals =	$953.57		$1,043.8109	$1,043.82	$1,043.85	$1,043.80