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	$62.40	13.508%	$70.829	$70.83	$70.85	$70.80
Purchase #2	$249.75	6.298%	$265.4793	$265.48	$265.50	$265.50
Purchase #3	$164.53	12.384%	$184.9054	$184.91	$184.90	$184.90
Purchase #4	$223.56	11.402%	$249.0503	$249.05	$249.05	$249.10
Purchase #5	$55.79	6.620%	$59.4833	$59.48	$59.50	$59.50
Purchase #6	$84.39	12.236%	$94.716	$94.72	$94.70	$94.70
Purchase #7	$173.47	8.617%	$188.4179	$188.42	$188.40	$188.40
7 purchase totals =	$1,013.89		$1,112.8812	$1,112.89	$1,112.90	$1,112.90