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	$16.78	5.122%	$17.6395	$17.64	$17.65	$17.60
Purchase #2	$59.41	5.196%	$62.4969	$62.50	$62.50	$62.50
Purchase #3	$230.68	5.325%	$242.9637	$242.96	$242.95	$243.00
Purchase #4	$173.27	13.120%	$196.003	$196.00	$196.00	$196.00
Purchase #5	$248.42	11.133%	$276.0766	$276.08	$276.10	$276.10
Purchase #6	$152.44	5.530%	$160.8699	$160.87	$160.85	$160.90
Purchase #7	$135.93	9.538%	$148.895	$148.90	$148.90	$148.90
7 purchase totals =	$1,016.93		$1,104.9446	$1,104.95	$1,104.95	$1,105.00