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	$199.79	7.732%	$215.2378	$215.24	$215.25	$215.20
Purchase #2	$66.75	8.631%	$72.5112	$72.51	$72.50	$72.50
Purchase #3	$165.73	6.427%	$176.3815	$176.38	$176.40	$176.40
Purchase #4	$227.41	7.707%	$244.9365	$244.94	$244.95	$244.90
Purchase #5	$245.51	12.758%	$276.8322	$276.83	$276.85	$276.80
Purchase #6	$162.27	3.830%	$168.4849	$168.48	$168.50	$168.50
Purchase #7	$142.68	9.653%	$156.4529	$156.45	$156.45	$156.50
7 purchase totals =	$1,210.14		$1,310.8370	$1,310.83	$1,310.90	$1,310.80