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	$53.91	11.495%	$60.107	$60.11	$60.10	$60.10
Purchase #2	$134.38	4.418%	$140.3169	$140.32	$140.30	$140.30
Purchase #3	$116.74	5.490%	$123.149	$123.15	$123.15	$123.10
Purchase #4	$46.28	11.260%	$51.4911	$51.49	$51.50	$51.50
Purchase #5	$181.70	5.299%	$191.3283	$191.33	$191.35	$191.30
Purchase #6	$50.89	8.665%	$55.2996	$55.30	$55.30	$55.30
Purchase #7	$96.52	7.739%	$103.9897	$103.99	$104.00	$104.00
7 purchase totals =	$680.42		$725.6816	$725.69	$725.70	$725.60