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	$186.30	10.175%	$205.256	$205.26	$205.25	$205.30
Purchase #2	$55.73	6.579%	$59.3965	$59.40	$59.40	$59.40
Purchase #3	$44.54	10.682%	$49.2978	$49.30	$49.30	$49.30
Purchase #4	$196.91	7.181%	$211.0501	$211.05	$211.05	$211.10
Purchase #5	$222.85	7.293%	$239.1025	$239.10	$239.10	$239.10
Purchase #6	$90.88	10.768%	$100.666	$100.67	$100.65	$100.70
Purchase #7	$109.51	11.206%	$121.7817	$121.78	$121.80	$121.80
7 purchase totals =	$906.72		$986.5506	$986.56	$986.55	$986.70