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	$50.58	6.539%	$53.8874	$53.89	$53.90	$53.90
Purchase #2	$209.38	3.210%	$216.1011	$216.10	$216.10	$216.10
Purchase #3	$37.99	11.703%	$42.436	$42.44	$42.45	$42.40
Purchase #4	$170.72	12.264%	$191.6571	$191.66	$191.65	$191.70
Purchase #5	$234.48	6.411%	$249.5125	$249.51	$249.50	$249.50
Purchase #6	$92.65	3.129%	$95.549	$95.55	$95.55	$95.50
Purchase #7	$171.86	7.214%	$184.258	$184.26	$184.25	$184.30
7 purchase totals =	$967.66		$1,033.4011	$1,033.41	$1,033.40	$1,033.40