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	$39.55	10.234%	$43.5975	$43.60	$43.60	$43.60
Purchase #2	$236.37	8.659%	$256.8373	$256.84	$256.85	$256.80
Purchase #3	$241.86	3.772%	$250.983	$250.98	$251.00	$251.00
Purchase #4	$162.33	13.369%	$184.0319	$184.03	$184.05	$184.00
Purchase #5	$107.73	3.811%	$111.8356	$111.84	$111.85	$111.80
Purchase #6	$147.40	6.431%	$156.8793	$156.88	$156.90	$156.90
Purchase #7	$96.47	7.345%	$103.5557	$103.56	$103.55	$103.60
7 purchase totals =	$1,031.71		$1,107.7203	$1,107.73	$1,107.80	$1,107.70