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	$59.39	3.389%	$61.4027	$61.40	$61.40	$61.40
Purchase #2	$140.80	13.840%	$160.2867	$160.29	$160.30	$160.30
Purchase #3	$186.34	12.195%	$209.0642	$209.06	$209.05	$209.10
Purchase #4	$62.48	11.159%	$69.4521	$69.45	$69.45	$69.50
Purchase #5	$155.59	11.362%	$173.2681	$173.27	$173.25	$173.30
Purchase #6	$179.55	8.221%	$194.3108	$194.31	$194.30	$194.30
Purchase #7	$236.37	3.600%	$244.8793	$244.88	$244.90	$244.90
7 purchase totals =	$1,020.52		$1,112.6639	$1,112.66	$1,112.65	$1,112.80