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	$45.32	3.119%	$46.7335	$46.73	$46.75	$46.70
Purchase #2	$104.30	5.229%	$109.7538	$109.75	$109.75	$109.80
Purchase #3	$131.43	4.436%	$137.2602	$137.26	$137.25	$137.30
Purchase #4	$49.48	7.106%	$52.996	$53.00	$53.00	$53.00
Purchase #5	$134.56	3.561%	$139.3517	$139.35	$139.35	$139.40
Purchase #6	$231.81	8.217%	$250.8578	$250.86	$250.85	$250.90
Purchase #7	$128.94	9.632%	$141.3595	$141.36	$141.35	$141.40
7 purchase totals =	$825.84		$878.3125	$878.31	$878.30	$878.50