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	$119.35	11.655%	$133.2602	$133.26	$133.25	$133.30
Purchase #2	$31.98	4.430%	$33.3967	$33.40	$33.40	$33.40
Purchase #3	$31.27	3.355%	$32.3191	$32.32	$32.30	$32.30
Purchase #4	$109.45	12.323%	$122.9375	$122.94	$122.95	$122.90
Purchase #5	$159.59	11.844%	$178.4918	$178.49	$178.50	$178.50
Purchase #6	$204.67	8.527%	$222.1222	$222.12	$222.10	$222.10
Purchase #7	$81.34	11.107%	$90.3744	$90.37	$90.35	$90.40
7 purchase totals =	$737.65		$812.9019	$812.90	$812.85	$812.90