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	$185.73	6.840%	$198.4339	$198.43	$198.45	$198.40
Purchase #2	$94.45	11.407%	$105.2239	$105.22	$105.20	$105.20
Purchase #3	$18.56	4.523%	$19.3995	$19.40	$19.40	$19.40
Purchase #4	$43.94	12.632%	$49.4905	$49.49	$49.50	$49.50
Purchase #5	$104.37	13.582%	$118.5455	$118.55	$118.55	$118.50
Purchase #6	$91.59	5.174%	$96.3289	$96.33	$96.35	$96.30
Purchase #7	$165.57	4.599%	$173.1846	$173.18	$173.20	$173.20
7 purchase totals =	$704.21		$760.6068	$760.60	$760.65	$760.50