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	$154.35	12.789%	$174.0898	$174.09	$174.10	$174.10
Purchase #2	$150.83	7.834%	$162.646	$162.65	$162.65	$162.60
Purchase #3	$166.88	11.460%	$186.0044	$186.00	$186.00	$186.00
Purchase #4	$28.47	11.224%	$31.6655	$31.67	$31.65	$31.70
Purchase #5	$70.92	10.663%	$78.4822	$78.48	$78.50	$78.50
Purchase #6	$237.52	6.538%	$253.0491	$253.05	$253.05	$253.00
Purchase #7	$114.38	10.284%	$126.1428	$126.14	$126.15	$126.10
7 purchase totals =	$923.35		$1,012.0798	$1,012.08	$1,012.10	$1,012.00