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	$31.61	7.340%	$33.9302	$33.93	$33.95	$33.90
Purchase #2	$98.86	12.688%	$111.4034	$111.40	$111.40	$111.40
Purchase #3	$114.51	12.413%	$128.7241	$128.72	$128.70	$128.70
Purchase #4	$102.36	6.172%	$108.6777	$108.68	$108.70	$108.70
Purchase #5	$95.54	11.669%	$106.6886	$106.69	$106.70	$106.70
Purchase #6	$54.72	5.815%	$57.902	$57.90	$57.90	$57.90
Purchase #7	$128.83	5.812%	$136.3176	$136.32	$136.30	$136.30
7 purchase totals =	$626.43		$683.6436	$683.64	$683.65	$683.60