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	$205.33	5.611%	$216.8511	$216.85	$216.85	$216.90
Purchase #2	$141.81	8.645%	$154.0695	$154.07	$154.05	$154.10
Purchase #3	$130.48	12.254%	$146.469	$146.47	$146.45	$146.50
Purchase #4	$103.55	5.631%	$109.3809	$109.38	$109.40	$109.40
Purchase #5	$223.73	8.452%	$242.6397	$242.64	$242.65	$242.60
Purchase #6	$102.45	7.689%	$110.3274	$110.33	$110.35	$110.30
Purchase #7	$31.72	6.414%	$33.7545	$33.75	$33.75	$33.80
7 purchase totals =	$939.07		$1,013.4921	$1,013.49	$1,013.50	$1,013.60