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	$212.56	9.674%	$233.1231	$233.12	$233.10	$233.10
Purchase #2	$103.88	7.181%	$111.3396	$111.34	$111.35	$111.30
Purchase #3	$117.93	8.686%	$128.1734	$128.17	$128.15	$128.20
Purchase #4	$123.86	4.699%	$129.6802	$129.68	$129.70	$129.70
Purchase #5	$151.97	7.208%	$162.924	$162.92	$162.90	$162.90
Purchase #6	$5.28	4.687%	$5.5275	$5.53	$5.55	$5.50
Purchase #7	$227.39	12.255%	$255.2566	$255.26	$255.25	$255.30
7 purchase totals =	$942.87		$1,026.0244	$1,026.02	$1,026.00	$1,026.00