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	$120.33	6.700%	$128.3921	$128.39	$128.40	$128.40
Purchase #2	$170.27	6.816%	$181.8756	$181.88	$181.90	$181.90
Purchase #3	$152.56	7.694%	$164.298	$164.30	$164.30	$164.30
Purchase #4	$250.33	12.621%	$281.9241	$281.92	$281.90	$281.90
Purchase #5	$148.58	6.786%	$158.6626	$158.66	$158.65	$158.70
Purchase #6	$15.89	3.438%	$16.4363	$16.44	$16.45	$16.40
Purchase #7	$139.47	10.519%	$154.1408	$154.14	$154.15	$154.10
7 purchase totals =	$997.43		$1,085.7295	$1,085.73	$1,085.75	$1,085.70