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	$87.90	13.431%	$99.7058	$99.71	$99.70	$99.70
Purchase #2	$240.69	13.549%	$273.3011	$273.30	$273.30	$273.30
Purchase #3	$179.66	11.515%	$200.3478	$200.35	$200.35	$200.30
Purchase #4	$97.34	8.722%	$105.83	$105.83	$105.85	$105.80
Purchase #5	$60.96	11.630%	$68.0496	$68.05	$68.05	$68.00
Purchase #6	$79.92	8.640%	$86.8251	$86.83	$86.85	$86.80
Purchase #7	$161.29	4.145%	$167.9755	$167.98	$168.00	$168.00
7 purchase totals =	$907.76		$1,002.0349	$1,002.05	$1,002.10	$1,001.90