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	$209.90	13.117%	$237.4326	$237.43	$237.45	$237.40
Purchase #2	$41.97	4.574%	$43.8897	$43.89	$43.90	$43.90
Purchase #3	$214.98	13.316%	$243.6067	$243.61	$243.60	$243.60
Purchase #4	$170.31	6.460%	$181.312	$181.31	$181.30	$181.30
Purchase #5	$61.97	3.573%	$64.1842	$64.18	$64.20	$64.20
Purchase #6	$173.88	5.745%	$183.8694	$183.87	$183.85	$183.90
Purchase #7	$156.34	11.627%	$174.5177	$174.52	$174.50	$174.50
7 purchase totals =	$1,029.35		$1,128.8123	$1,128.81	$1,128.80	$1,128.80