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	$191.96	8.282%	$207.8581	$207.86	$207.85	$207.90
Purchase #2	$214.87	8.837%	$233.8581	$233.86	$233.85	$233.90
Purchase #3	$50.96	11.185%	$56.6599	$56.66	$56.65	$56.70
Purchase #4	$135.83	7.471%	$145.9779	$145.98	$146.00	$146.00
Purchase #5	$202.38	9.731%	$222.0736	$222.07	$222.05	$222.10
Purchase #6	$72.41	10.405%	$79.9443	$79.94	$79.95	$79.90
Purchase #7	$188.34	4.555%	$196.9189	$196.92	$196.90	$196.90
7 purchase totals =	$1,056.75		$1,143.2908	$1,143.29	$1,143.25	$1,143.40