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	$185.94	4.322%	$193.9763	$193.98	$194.00	$194.00
Purchase #2	$119.75	6.632%	$127.6918	$127.69	$127.70	$127.70
Purchase #3	$27.44	3.746%	$28.4679	$28.47	$28.45	$28.50
Purchase #4	$21.64	5.624%	$22.857	$22.86	$22.85	$22.90
Purchase #5	$232.89	13.476%	$264.2743	$264.27	$264.25	$264.30
Purchase #6	$66.81	3.647%	$69.2466	$69.25	$69.25	$69.20
Purchase #7	$155.83	10.288%	$171.8618	$171.86	$171.85	$171.90
7 purchase totals =	$810.30		$878.3757	$878.38	$878.35	$878.50