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	$92.47	9.559%	$101.3092	$101.31	$101.30	$101.30
Purchase #2	$77.84	11.699%	$86.9465	$86.95	$86.95	$86.90
Purchase #3	$128.86	9.871%	$141.5798	$141.58	$141.60	$141.60
Purchase #4	$95.73	4.328%	$99.8732	$99.87	$99.85	$99.90
Purchase #5	$140.26	3.595%	$145.3023	$145.30	$145.30	$145.30
Purchase #6	$93.41	10.626%	$103.3357	$103.34	$103.35	$103.30
Purchase #7	$235.33	12.434%	$264.5909	$264.59	$264.60	$264.60
7 purchase totals =	$863.90		$942.9376	$942.94	$942.95	$942.90