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	$99.55	9.868%	$109.3736	$109.37	$109.35	$109.40
Purchase #2	$27.96	10.360%	$30.8567	$30.86	$30.85	$30.90
Purchase #3	$239.88	13.132%	$271.381	$271.38	$271.40	$271.40
Purchase #4	$122.54	8.771%	$133.288	$133.29	$133.30	$133.30
Purchase #5	$78.50	4.475%	$82.0129	$82.01	$82.00	$82.00
Purchase #6	$250.29	10.626%	$276.8858	$276.89	$276.90	$276.90
Purchase #7	$139.83	8.809%	$152.1476	$152.15	$152.15	$152.10
7 purchase totals =	$958.55		$1,055.9456	$1,055.95	$1,055.95	$1,056.00