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	$135.78	8.714%	$147.6119	$147.61	$147.60	$147.60
Purchase #2	$73.82	4.706%	$77.294	$77.29	$77.30	$77.30
Purchase #3	$64.27	13.683%	$73.0641	$73.06	$73.05	$73.10
Purchase #4	$67.37	6.267%	$71.5921	$71.59	$71.60	$71.60
Purchase #5	$112.64	7.271%	$120.8301	$120.83	$120.85	$120.80
Purchase #6	$87.66	3.554%	$90.7754	$90.78	$90.80	$90.80
Purchase #7	$174.79	10.168%	$192.5626	$192.56	$192.55	$192.60
7 purchase totals =	$716.33		$773.7302	$773.72	$773.75	$773.80