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	$84.79	6.547%	$90.3412	$90.34	$90.35	$90.30
Purchase #2	$245.39	8.534%	$266.3316	$266.33	$266.35	$266.30
Purchase #3	$99.32	9.390%	$108.6461	$108.65	$108.65	$108.60
Purchase #4	$223.52	4.528%	$233.641	$233.64	$233.65	$233.60
Purchase #5	$72.27	6.428%	$76.9155	$76.92	$76.90	$76.90
Purchase #6	$192.90	7.509%	$207.3849	$207.38	$207.40	$207.40
Purchase #7	$111.64	6.107%	$118.4579	$118.46	$118.45	$118.50
7 purchase totals =	$1,029.83		$1,101.7182	$1,101.72	$1,101.75	$1,101.60