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	$181.89	8.157%	$196.7268	$196.73	$196.75	$196.70
Purchase #2	$123.25	11.706%	$137.6776	$137.68	$137.70	$137.70
Purchase #3	$48.62	11.319%	$54.1233	$54.12	$54.10	$54.10
Purchase #4	$175.35	10.361%	$193.518	$193.52	$193.50	$193.50
Purchase #5	$178.37	5.109%	$187.4829	$187.48	$187.50	$187.50
Purchase #6	$160.92	4.587%	$168.3014	$168.30	$168.30	$168.30
Purchase #7	$75.38	10.212%	$83.0778	$83.08	$83.10	$83.10
7 purchase totals =	$943.78		$1,020.9078	$1,020.91	$1,020.95	$1,020.90