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	$150.62	4.164%	$156.8918	$156.89	$156.90	$156.90
Purchase #2	$233.37	12.752%	$263.1293	$263.13	$263.15	$263.10
Purchase #3	$137.69	5.175%	$144.8155	$144.82	$144.80	$144.80
Purchase #4	$45.26	13.449%	$51.347	$51.35	$51.35	$51.30
Purchase #5	$57.32	6.541%	$61.0693	$61.07	$61.05	$61.10
Purchase #6	$238.58	12.492%	$268.3834	$268.38	$268.40	$268.40
Purchase #7	$102.63	11.739%	$114.6777	$114.68	$114.70	$114.70
7 purchase totals =	$965.47		$1,060.3140	$1,060.32	$1,060.35	$1,060.30