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	$67.31	3.289%	$69.5238	$69.52	$69.50	$69.50
Purchase #2	$54.46	13.651%	$61.8943	$61.89	$61.90	$61.90
Purchase #3	$148.57	6.819%	$158.701	$158.70	$158.70	$158.70
Purchase #4	$184.38	7.860%	$198.8723	$198.87	$198.85	$198.90
Purchase #5	$178.43	4.297%	$186.0971	$186.10	$186.10	$186.10
Purchase #6	$181.61	8.310%	$196.7018	$196.70	$196.70	$196.70
Purchase #7	$79.50	8.297%	$86.0961	$86.10	$86.10	$86.10
7 purchase totals =	$894.26		$957.8864	$957.88	$957.85	$957.90