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	$190.43	10.714%	$210.8327	$210.83	$210.85	$210.80
Purchase #2	$104.28	5.350%	$109.859	$109.86	$109.85	$109.90
Purchase #3	$180.57	11.702%	$201.7003	$201.70	$201.70	$201.70
Purchase #4	$33.55	8.250%	$36.3179	$36.32	$36.30	$36.30
Purchase #5	$119.41	6.363%	$127.0081	$127.01	$127.00	$127.00
Purchase #6	$131.57	4.744%	$137.8117	$137.81	$137.80	$137.80
Purchase #7	$43.56	5.360%	$45.8948	$45.89	$45.90	$45.90
7 purchase totals =	$803.37		$869.4245	$869.42	$869.40	$869.40