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	$188.41	5.443%	$198.6652	$198.67	$198.65	$198.70
Purchase #2	$90.36	11.369%	$100.633	$100.63	$100.65	$100.60
Purchase #3	$164.77	12.678%	$185.6595	$185.66	$185.65	$185.70
Purchase #4	$165.30	4.699%	$173.0674	$173.07	$173.05	$173.10
Purchase #5	$242.32	8.663%	$263.3122	$263.31	$263.30	$263.30
Purchase #6	$92.29	11.869%	$103.2439	$103.24	$103.25	$103.20
Purchase #7	$105.27	6.866%	$112.4978	$112.50	$112.50	$112.50
7 purchase totals =	$1,048.72		$1,137.0790	$1,137.08	$1,137.05	$1,137.10