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	$164.42	10.618%	$181.8781	$181.88	$181.90	$181.90
Purchase #2	$243.87	6.742%	$260.3117	$260.31	$260.30	$260.30
Purchase #3	$40.87	6.426%	$43.4963	$43.50	$43.50	$43.50
Purchase #4	$96.36	12.608%	$108.5091	$108.51	$108.50	$108.50
Purchase #5	$90.41	6.451%	$96.2423	$96.24	$96.25	$96.20
Purchase #6	$77.30	8.560%	$83.9169	$83.92	$83.90	$83.90
Purchase #7	$173.39	10.343%	$191.3237	$191.32	$191.30	$191.30
7 purchase totals =	$886.62		$965.6781	$965.68	$965.65	$965.60