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	$220.55	3.620%	$228.5339	$228.53	$228.55	$228.50
Purchase #2	$229.48	5.687%	$242.5305	$242.53	$242.55	$242.50
Purchase #3	$208.61	9.727%	$228.9015	$228.90	$228.90	$228.90
Purchase #4	$201.40	8.432%	$218.382	$218.38	$218.40	$218.40
Purchase #5	$37.64	8.453%	$40.8217	$40.82	$40.80	$40.80
Purchase #6	$238.57	9.521%	$261.2842	$261.28	$261.30	$261.30
Purchase #7	$83.89	6.717%	$89.5249	$89.52	$89.50	$89.50
7 purchase totals =	$1,220.14		$1,309.9787	$1,309.96	$1,310.00	$1,309.90