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	$160.63	5.144%	$168.8928	$168.89	$168.90	$168.90
Purchase #2	$91.46	10.192%	$100.7816	$100.78	$100.80	$100.80
Purchase #3	$189.80	8.424%	$205.7888	$205.79	$205.80	$205.80
Purchase #4	$131.52	13.234%	$148.9254	$148.93	$148.95	$148.90
Purchase #5	$241.46	5.501%	$254.7427	$254.74	$254.75	$254.70
Purchase #6	$120.58	9.618%	$132.1774	$132.18	$132.20	$132.20
Purchase #7	$64.51	12.358%	$72.4821	$72.48	$72.50	$72.50
7 purchase totals =	$999.96		$1,083.7908	$1,083.79	$1,083.90	$1,083.80