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	$153.90	12.241%	$172.7389	$172.74	$172.75	$172.70
Purchase #2	$170.35	12.301%	$191.3048	$191.30	$191.30	$191.30
Purchase #3	$155.39	3.541%	$160.8924	$160.89	$160.90	$160.90
Purchase #4	$54.54	9.535%	$59.7404	$59.74	$59.75	$59.70
Purchase #5	$172.50	5.736%	$182.3946	$182.39	$182.40	$182.40
Purchase #6	$158.41	3.347%	$163.712	$163.71	$163.70	$163.70
Purchase #7	$79.31	4.575%	$82.9384	$82.94	$82.95	$82.90
7 purchase totals =	$944.40		$1,013.7215	$1,013.71	$1,013.75	$1,013.60