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	$142.88	6.627%	$152.3487	$152.35	$152.35	$152.30
Purchase #2	$56.39	8.848%	$61.3794	$61.38	$61.40	$61.40
Purchase #3	$178.85	7.393%	$192.0724	$192.07	$192.05	$192.10
Purchase #4	$197.72	7.224%	$212.0033	$212.00	$212.00	$212.00
Purchase #5	$217.41	7.451%	$233.6092	$233.61	$233.60	$233.60
Purchase #6	$30.79	6.423%	$32.7676	$32.77	$32.75	$32.80
Purchase #7	$226.75	7.203%	$243.0828	$243.08	$243.10	$243.10
7 purchase totals =	$1,050.79		$1,127.2634	$1,127.26	$1,127.25	$1,127.30