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	$41.56	6.150%	$44.1159	$44.12	$44.10	$44.10
Purchase #2	$81.56	9.846%	$89.5904	$89.59	$89.60	$89.60
Purchase #3	$24.45	3.800%	$25.3791	$25.38	$25.40	$25.40
Purchase #4	$198.81	13.768%	$226.1822	$226.18	$226.20	$226.20
Purchase #5	$243.75	8.245%	$263.8472	$263.85	$263.85	$263.80
Purchase #6	$168.45	12.545%	$189.5821	$189.58	$189.60	$189.60
Purchase #7	$218.36	7.119%	$233.905	$233.91	$233.90	$233.90
7 purchase totals =	$976.94		$1,072.6019	$1,072.61	$1,072.65	$1,072.60