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	$152.68	5.683%	$161.3568	$161.36	$161.35	$161.40
Purchase #2	$100.82	4.400%	$105.2561	$105.26	$105.25	$105.30
Purchase #3	$135.52	4.107%	$141.0858	$141.09	$141.10	$141.10
Purchase #4	$123.45	6.134%	$131.0224	$131.02	$131.00	$131.00
Purchase #5	$183.44	13.751%	$208.6648	$208.66	$208.65	$208.70
Purchase #6	$69.32	13.534%	$78.7018	$78.70	$78.70	$78.70
Purchase #7	$62.60	7.537%	$67.3182	$67.32	$67.30	$67.30
7 purchase totals =	$827.83		$893.4059	$893.41	$893.35	$893.50