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	$41.69	3.412%	$43.1125	$43.11	$43.10	$43.10
Purchase #2	$99.58	5.274%	$104.8318	$104.83	$104.85	$104.80
Purchase #3	$177.89	6.742%	$189.8833	$189.88	$189.90	$189.90
Purchase #4	$205.72	11.539%	$229.458	$229.46	$229.45	$229.50
Purchase #5	$152.99	12.845%	$172.6416	$172.64	$172.65	$172.60
Purchase #6	$236.42	6.827%	$252.5604	$252.56	$252.55	$252.60
Purchase #7	$115.25	13.552%	$130.8687	$130.87	$130.85	$130.90
7 purchase totals =	$1,029.54		$1,123.3563	$1,123.35	$1,123.35	$1,123.40