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	$178.55	9.774%	$196.0015	$196.00	$196.00	$196.00
Purchase #2	$116.61	9.852%	$128.0984	$128.10	$128.10	$128.10
Purchase #3	$127.91	7.767%	$137.8448	$137.84	$137.85	$137.80
Purchase #4	$167.68	12.726%	$189.019	$189.02	$189.00	$189.00
Purchase #5	$60.76	8.115%	$65.6907	$65.69	$65.70	$65.70
Purchase #6	$81.74	11.411%	$91.0674	$91.07	$91.05	$91.10
Purchase #7	$156.32	10.280%	$172.3897	$172.39	$172.40	$172.40
7 purchase totals =	$889.57		$980.1115	$980.11	$980.10	$980.10