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	$59.65	5.228%	$62.7685	$62.77	$62.75	$62.80
Purchase #2	$220.58	10.677%	$244.1313	$244.13	$244.15	$244.10
Purchase #3	$178.37	5.630%	$188.4122	$188.41	$188.40	$188.40
Purchase #4	$113.52	5.216%	$119.4412	$119.44	$119.45	$119.40
Purchase #5	$43.90	6.823%	$46.8953	$46.90	$46.90	$46.90
Purchase #6	$58.41	10.666%	$64.64	$64.64	$64.65	$64.60
Purchase #7	$76.54	8.839%	$83.3054	$83.31	$83.30	$83.30
7 purchase totals =	$750.97		$809.5939	$809.60	$809.60	$809.50