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	$210.27	11.201%	$233.8223	$233.82	$233.80	$233.80
Purchase #2	$7.40	11.739%	$8.2687	$8.27	$8.25	$8.30
Purchase #3	$53.25	10.550%	$58.8679	$58.87	$58.85	$58.90
Purchase #4	$70.68	11.713%	$78.9587	$78.96	$78.95	$79.00
Purchase #5	$78.73	13.500%	$89.3586	$89.36	$89.35	$89.40
Purchase #6	$138.88	4.198%	$144.7102	$144.71	$144.70	$144.70
Purchase #7	$216.63	7.727%	$233.369	$233.37	$233.35	$233.40
7 purchase totals =	$775.84		$847.3554	$847.36	$847.25	$847.50