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	$214.79	3.481%	$222.2668	$222.27	$222.25	$222.30
Purchase #2	$101.91	7.390%	$109.4411	$109.44	$109.45	$109.40
Purchase #3	$68.52	6.412%	$72.9135	$72.91	$72.90	$72.90
Purchase #4	$50.53	9.412%	$55.2859	$55.29	$55.30	$55.30
Purchase #5	$131.67	3.569%	$136.3693	$136.37	$136.35	$136.40
Purchase #6	$242.79	11.309%	$270.2471	$270.25	$270.25	$270.20
Purchase #7	$29.79	6.597%	$31.7552	$31.76	$31.75	$31.80
7 purchase totals =	$840.00		$898.2789	$898.29	$898.25	$898.30