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	$125.83	13.458%	$142.7642	$142.76	$142.75	$142.80
Purchase #2	$210.77	5.630%	$222.6364	$222.64	$222.65	$222.60
Purchase #3	$132.69	10.275%	$146.3239	$146.32	$146.30	$146.30
Purchase #4	$54.28	3.534%	$56.1983	$56.20	$56.20	$56.20
Purchase #5	$240.53	5.834%	$254.5625	$254.56	$254.55	$254.60
Purchase #6	$128.60	4.793%	$134.7638	$134.76	$134.75	$134.80
Purchase #7	$56.26	13.199%	$63.6858	$63.69	$63.70	$63.70
7 purchase totals =	$948.96		$1,020.9349	$1,020.93	$1,020.90	$1,021.00