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	$105.95	9.380%	$115.8881	$115.89	$115.90	$115.90
Purchase #2	$161.66	5.790%	$171.0201	$171.02	$171.00	$171.00
Purchase #3	$62.65	5.711%	$66.2279	$66.23	$66.25	$66.20
Purchase #4	$156.74	9.601%	$171.7886	$171.79	$171.80	$171.80
Purchase #5	$163.31	4.825%	$171.1897	$171.19	$171.20	$171.20
Purchase #6	$189.59	4.760%	$198.6145	$198.61	$198.60	$198.60
Purchase #7	$221.66	5.232%	$233.2573	$233.26	$233.25	$233.30
7 purchase totals =	$1,061.56		$1,127.9862	$1,127.99	$1,128.00	$1,128.00