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	$188.79	6.157%	$200.4138	$200.41	$200.40	$200.40
Purchase #2	$111.44	4.590%	$116.5551	$116.56	$116.55	$116.60
Purchase #3	$220.60	5.869%	$233.547	$233.55	$233.55	$233.50
Purchase #4	$51.63	8.378%	$55.9556	$55.96	$55.95	$56.00
Purchase #5	$84.39	8.629%	$91.672	$91.67	$91.65	$91.70
Purchase #6	$228.42	4.221%	$238.0616	$238.06	$238.05	$238.10
Purchase #7	$136.49	13.205%	$154.5135	$154.51	$154.50	$154.50
7 purchase totals =	$1,021.76		$1,090.7186	$1,090.72	$1,090.65	$1,090.80