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	$165.48	3.683%	$171.5746	$171.57	$171.55	$171.60
Purchase #2	$223.91	7.507%	$240.7189	$240.72	$240.70	$240.70
Purchase #3	$33.85	10.657%	$37.4574	$37.46	$37.45	$37.50
Purchase #4	$42.46	12.650%	$47.8312	$47.83	$47.85	$47.80
Purchase #5	$47.45	10.135%	$52.2591	$52.26	$52.25	$52.30
Purchase #6	$79.85	5.436%	$84.1906	$84.19	$84.20	$84.20
Purchase #7	$59.72	9.407%	$65.3379	$65.34	$65.35	$65.30
7 purchase totals =	$652.72		$699.3697	$699.37	$699.35	$699.40