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	$179.47	8.549%	$194.8129	$194.81	$194.80	$194.80
Purchase #2	$102.95	6.666%	$109.8126	$109.81	$109.80	$109.80
Purchase #3	$186.57	12.279%	$209.4789	$209.48	$209.50	$209.50
Purchase #4	$97.49	3.639%	$101.0377	$101.04	$101.05	$101.00
Purchase #5	$221.94	6.340%	$236.011	$236.01	$236.00	$236.00
Purchase #6	$82.50	3.483%	$85.3735	$85.37	$85.35	$85.40
Purchase #7	$156.68	7.806%	$168.9104	$168.91	$168.90	$168.90
7 purchase totals =	$1,027.60		$1,105.4370	$1,105.43	$1,105.40	$1,105.40