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	$215.66	7.839%	$232.5656	$232.57	$232.55	$232.60
Purchase #2	$40.27	11.504%	$44.9027	$44.90	$44.90	$44.90
Purchase #3	$69.79	13.152%	$78.9688	$78.97	$78.95	$79.00
Purchase #4	$86.73	3.662%	$89.9061	$89.91	$89.90	$89.90
Purchase #5	$188.35	7.191%	$201.8942	$201.89	$201.90	$201.90
Purchase #6	$39.45	6.769%	$42.1204	$42.12	$42.10	$42.10
Purchase #7	$240.66	4.690%	$251.947	$251.95	$251.95	$251.90
7 purchase totals =	$880.91		$942.3048	$942.31	$942.25	$942.30