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	$90.86	7.853%	$97.9952	$98.00	$98.00	$98.00
Purchase #2	$53.69	7.792%	$57.8735	$57.87	$57.85	$57.90
Purchase #3	$216.65	5.255%	$228.035	$228.04	$228.05	$228.00
Purchase #4	$64.98	3.487%	$67.2459	$67.25	$67.25	$67.20
Purchase #5	$9.75	8.706%	$10.5988	$10.60	$10.60	$10.60
Purchase #6	$100.82	4.451%	$105.3075	$105.31	$105.30	$105.30
Purchase #7	$156.64	3.614%	$162.301	$162.30	$162.30	$162.30
7 purchase totals =	$693.39		$729.3569	$729.37	$729.35	$729.30