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	$176.82	4.355%	$184.5205	$184.52	$184.50	$184.50
Purchase #2	$93.64	13.407%	$106.1943	$106.19	$106.20	$106.20
Purchase #3	$223.86	4.295%	$233.4748	$233.47	$233.45	$233.50
Purchase #4	$215.70	11.719%	$240.9779	$240.98	$241.00	$241.00
Purchase #5	$154.94	6.826%	$165.5162	$165.52	$165.50	$165.50
Purchase #6	$94.66	4.349%	$98.7768	$98.78	$98.80	$98.80
Purchase #7	$196.27	4.790%	$205.6713	$205.67	$205.65	$205.70
7 purchase totals =	$1,155.89		$1,235.1318	$1,235.13	$1,235.10	$1,235.20