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	$129.63	9.347%	$141.7465	$141.75	$141.75	$141.70
Purchase #2	$36.74	6.287%	$39.0498	$39.05	$39.05	$39.00
Purchase #3	$56.63	5.803%	$59.9162	$59.92	$59.90	$59.90
Purchase #4	$59.73	12.715%	$67.3247	$67.32	$67.30	$67.30
Purchase #5	$195.63	10.438%	$216.0499	$216.05	$216.05	$216.00
Purchase #6	$75.32	9.292%	$82.3187	$82.32	$82.30	$82.30
Purchase #7	$171.55	3.802%	$178.0723	$178.07	$178.05	$178.10
7 purchase totals =	$725.23		$784.4781	$784.48	$784.40	$784.30