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	$184.79	6.501%	$196.8032	$196.80	$196.80	$196.80
Purchase #2	$225.60	5.709%	$238.4795	$238.48	$238.50	$238.50
Purchase #3	$57.34	10.104%	$63.1336	$63.13	$63.15	$63.10
Purchase #4	$79.30	5.844%	$83.9343	$83.93	$83.95	$83.90
Purchase #5	$25.47	9.338%	$27.8484	$27.85	$27.85	$27.80
Purchase #6	$174.85	7.665%	$188.2523	$188.25	$188.25	$188.30
Purchase #7	$238.50	3.572%	$247.0192	$247.02	$247.00	$247.00
7 purchase totals =	$985.85		$1,045.4705	$1,045.46	$1,045.50	$1,045.40