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	$142.74	9.455%	$156.2361	$156.24	$156.25	$156.20
Purchase #2	$211.91	9.271%	$231.5562	$231.56	$231.55	$231.60
Purchase #3	$60.77	13.365%	$68.8919	$68.89	$68.90	$68.90
Purchase #4	$106.83	8.626%	$116.0452	$116.05	$116.05	$116.00
Purchase #5	$235.35	11.272%	$261.8787	$261.88	$261.90	$261.90
Purchase #6	$89.49	10.115%	$98.5419	$98.54	$98.55	$98.50
Purchase #7	$66.63	8.803%	$72.4954	$72.50	$72.50	$72.50
7 purchase totals =	$913.72		$1,005.6454	$1,005.66	$1,005.70	$1,005.60