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	$98.56	7.600%	$106.0506	$106.05	$106.05	$106.10
Purchase #2	$53.28	11.636%	$59.4797	$59.48	$59.50	$59.50
Purchase #3	$47.38	5.506%	$49.9887	$49.99	$50.00	$50.00
Purchase #4	$137.58	10.759%	$152.3822	$152.38	$152.40	$152.40
Purchase #5	$89.38	13.597%	$101.533	$101.53	$101.55	$101.50
Purchase #6	$241.88	6.372%	$257.2926	$257.29	$257.30	$257.30
Purchase #7	$96.32	3.852%	$100.0302	$100.03	$100.05	$100.00
7 purchase totals =	$764.38		$826.7570	$826.75	$826.85	$826.80