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	$60.36	8.566%	$65.5304	$65.53	$65.55	$65.50
Purchase #2	$64.73	10.661%	$71.6309	$71.63	$71.65	$71.60
Purchase #3	$38.44	9.578%	$42.1218	$42.12	$42.10	$42.10
Purchase #4	$181.96	13.650%	$206.7975	$206.80	$206.80	$206.80
Purchase #5	$170.61	6.527%	$181.7457	$181.75	$181.75	$181.70
Purchase #6	$183.26	6.106%	$194.4499	$194.45	$194.45	$194.40
Purchase #7	$82.81	8.210%	$89.6087	$89.61	$89.60	$89.60
7 purchase totals =	$782.17		$851.8849	$851.89	$851.90	$851.70