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	$144.63	5.309%	$152.3084	$152.31	$152.30	$152.30
Purchase #2	$46.89	5.574%	$49.5036	$49.50	$49.50	$49.50
Purchase #3	$176.62	6.778%	$188.5913	$188.59	$188.60	$188.60
Purchase #4	$5.56	13.175%	$6.2925	$6.29	$6.30	$6.30
Purchase #5	$192.46	13.597%	$218.6288	$218.63	$218.65	$218.60
Purchase #6	$169.39	8.785%	$184.2709	$184.27	$184.25	$184.30
Purchase #7	$96.59	3.424%	$99.8972	$99.90	$99.90	$99.90
7 purchase totals =	$832.14		$899.4927	$899.49	$899.50	$899.50