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	$170.80	6.291%	$181.545	$181.55	$181.55	$181.50
Purchase #2	$182.69	4.454%	$190.827	$190.83	$190.85	$190.80
Purchase #3	$216.48	3.264%	$223.5459	$223.55	$223.55	$223.50
Purchase #4	$127.33	11.684%	$142.2072	$142.21	$142.20	$142.20
Purchase #5	$43.84	8.504%	$47.5682	$47.57	$47.55	$47.60
Purchase #6	$129.52	13.815%	$147.4132	$147.41	$147.40	$147.40
Purchase #7	$207.92	5.399%	$219.1456	$219.15	$219.15	$219.10
7 purchase totals =	$1,078.58		$1,152.2521	$1,152.27	$1,152.25	$1,152.10