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	$188.30	4.509%	$196.7904	$196.79	$196.80	$196.80
Purchase #2	$176.50	7.522%	$189.7763	$189.78	$189.80	$189.80
Purchase #3	$39.38	7.467%	$42.3205	$42.32	$42.30	$42.30
Purchase #4	$182.82	12.556%	$205.7749	$205.77	$205.75	$205.80
Purchase #5	$233.30	4.227%	$243.1616	$243.16	$243.15	$243.20
Purchase #6	$29.50	7.599%	$31.7417	$31.74	$31.75	$31.70
Purchase #7	$186.62	13.541%	$211.8902	$211.89	$211.90	$211.90
7 purchase totals =	$1,036.42		$1,121.4556	$1,121.45	$1,121.45	$1,121.50