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	$157.94	8.234%	$170.9448	$170.94	$170.95	$170.90
Purchase #2	$143.87	12.832%	$162.3314	$162.33	$162.35	$162.30
Purchase #3	$171.74	8.459%	$186.2675	$186.27	$186.25	$186.30
Purchase #4	$144.66	9.593%	$158.5372	$158.54	$158.55	$158.50
Purchase #5	$128.58	6.115%	$136.4427	$136.44	$136.45	$136.40
Purchase #6	$43.49	12.451%	$48.9049	$48.90	$48.90	$48.90
Purchase #7	$133.94	4.151%	$139.4998	$139.50	$139.50	$139.50
7 purchase totals =	$924.22		$1,002.9283	$1,002.92	$1,002.95	$1,002.80