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	$178.86	3.673%	$185.4295	$185.43	$185.45	$185.40
Purchase #2	$98.66	6.280%	$104.8558	$104.86	$104.85	$104.90
Purchase #3	$14.57	7.282%	$15.631	$15.63	$15.65	$15.60
Purchase #4	$133.26	5.152%	$140.1256	$140.13	$140.15	$140.10
Purchase #5	$88.69	13.317%	$100.5008	$100.50	$100.50	$100.50
Purchase #6	$49.83	12.529%	$56.0732	$56.07	$56.05	$56.10
Purchase #7	$184.96	5.295%	$194.7536	$194.75	$194.75	$194.80
7 purchase totals =	$748.83		$797.3695	$797.37	$797.40	$797.40