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	$141.42	10.519%	$156.296	$156.30	$156.30	$156.30
Purchase #2	$9.92	12.352%	$11.1453	$11.15	$11.15	$11.10
Purchase #3	$39.65	6.771%	$42.3347	$42.33	$42.35	$42.30
Purchase #4	$75.55	10.569%	$83.5349	$83.53	$83.55	$83.50
Purchase #5	$136.44	5.427%	$143.8446	$143.84	$143.85	$143.80
Purchase #6	$44.98	11.501%	$50.1531	$50.15	$50.15	$50.20
Purchase #7	$168.65	11.194%	$187.5287	$187.53	$187.55	$187.50
7 purchase totals =	$616.61		$674.8373	$674.83	$674.90	$674.70