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	$188.76	12.509%	$212.372	$212.37	$212.35	$212.40
Purchase #2	$80.67	5.532%	$85.1327	$85.13	$85.15	$85.10
Purchase #3	$142.56	11.361%	$158.7562	$158.76	$158.75	$158.80
Purchase #4	$173.58	5.633%	$183.3578	$183.36	$183.35	$183.40
Purchase #5	$128.62	12.377%	$144.5393	$144.54	$144.55	$144.50
Purchase #6	$238.61	12.565%	$268.5913	$268.59	$268.60	$268.60
Purchase #7	$142.38	3.833%	$147.8374	$147.84	$147.85	$147.80
7 purchase totals =	$1,095.18		$1,200.5867	$1,200.59	$1,200.60	$1,200.60