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	$98.80	11.179%	$109.8449	$109.84	$109.85	$109.80
Purchase #2	$85.95	3.858%	$89.266	$89.27	$89.25	$89.30
Purchase #3	$59.89	12.411%	$67.3229	$67.32	$67.30	$67.30
Purchase #4	$17.85	3.374%	$18.4523	$18.45	$18.45	$18.50
Purchase #5	$159.63	5.699%	$168.7273	$168.73	$168.75	$168.70
Purchase #6	$128.33	9.430%	$140.4315	$140.43	$140.45	$140.40
Purchase #7	$179.66	7.185%	$192.5686	$192.57	$192.55	$192.60
7 purchase totals =	$730.11		$786.6135	$786.61	$786.60	$786.60