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	$238.83	7.216%	$256.064	$256.06	$256.05	$256.10
Purchase #2	$70.63	13.144%	$79.9136	$79.91	$79.90	$79.90
Purchase #3	$238.36	13.788%	$271.2251	$271.23	$271.25	$271.20
Purchase #4	$64.92	6.123%	$68.8951	$68.90	$68.90	$68.90
Purchase #5	$97.81	8.345%	$105.9722	$105.97	$105.95	$106.00
Purchase #6	$202.69	10.273%	$223.5123	$223.51	$223.50	$223.50
Purchase #7	$84.36	12.457%	$94.8687	$94.87	$94.85	$94.90
7 purchase totals =	$997.60		$1,100.4510	$1,100.45	$1,100.40	$1,100.50