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	$83.39	13.400%	$94.5643	$94.56	$94.55	$94.60
Purchase #2	$59.61	4.445%	$62.2597	$62.26	$62.25	$62.30
Purchase #3	$156.64	11.186%	$174.1618	$174.16	$174.15	$174.20
Purchase #4	$150.55	9.287%	$164.5316	$164.53	$164.55	$164.50
Purchase #5	$123.67	13.742%	$140.6647	$140.66	$140.65	$140.70
Purchase #6	$196.47	11.595%	$219.2507	$219.25	$219.25	$219.30
Purchase #7	$216.43	3.360%	$223.702	$223.70	$223.70	$223.70
7 purchase totals =	$986.76		$1,079.1348	$1,079.12	$1,079.10	$1,079.30